The last gas question

[Tonavi]

I know octane and gas questions have been covered elsewhere on the forum, but in all of those threads there isn't a clear answer on the subject.

I bought my hatch in August 2007, and from the day I drove it home on the first dealer-bought tank of gas, noticed what sounded like a valvetrain rattle or something like that. I continued to put in regular 87 octane gas and the car kept rattling, and it was very easy to hear with the windows down.

After talking to a mechanical engineer, I tried using the 89 octane stuff to quiet things down, and the car runs noticeably smoother and is silent. My first tank of 89 was at 1600 miles, and now I'm at almost 21,000.

I was reading a Fit forum on FE when I read a post that was about how using higher octane gas could slowly wreck your motor over time by burning too hot and causing timing problems. That's when I went on Google and started researching. Let me note that switching from 87 to 89 resulted in no gain in mileage that probably wasn't related to the break in period. I get between 38 and 44 normally.

Is it true that using +2 octane gas causes carbon buildup and such? If that's the case, wouldn't running Seafoam every 10,000 miles keep things clean and more efficient? If anything, premium is a waste of money, but the extra $0.03 seems to make a difference in the drive.

[ChinoCharles]

The bottom line is that Toyota designed this car for regular old 87 pump gas. Says it in the owner's manual.

[Tonavi]

The bottom line is that Toyota designed this car for regular old 87 pump gas. Says it in the owner's manual.

Specifically, the manual says "minimum required." So that must mean that using a grade higher will do no harm? Not like I'm using race gas or anything.

[ChinoCharles]

AH! Semantics. Does that mean minimum required, like, put at least 87 in it, or does it mean minimum required, ie: it requires the minimum.

The real, meaningful answer: I don't know one Toyota engineer that belongs to Yarisworld. Take the rest of this thread with a big, giant grain of salt and do what makes YOU happy. :smile:

[PetersRedYaris]

AH! Semantics. Does that mean minimum required, like, put at least 87 in it, or does it mean minimum required, ie: it requires the minimum... :smile:

I would think it means "put at least 87 in it", since many parts of the country have grades far below 87 octane. 85 is the low here...

[Tonavi]

I guess the only way to test it is to run some seafoam through the vacuum line and judge the carbon by the smoke....

It would be interesting how dirty a car can get in 21,000 miles regardless of fuel type though...

[ChinoCharles]

It was a joke, Peter. Jeez.

[PetersRedYaris]

:redface::iono::redface:

[Tamago]

AH! Semantics. Does that mean minimum required, like, put at least 87 in it, or does it mean minimum required, ie: it requires the minimum.

The real, meaningful answer: I don't know one Toyota engineer that belongs to Yarisworld. Take the rest of this thread with a big, giant grain of salt and do what makes YOU happy. :smile:


well since 87 is the minimum available how would you put a lower octane fuel in the car?

[Tamago]

I would think it means "put at least 87 in it", since many parts of the country have grades far below 87 octane. 85 is the low here...

where can one get 85?

[frownonfun]

here

[1NZYaris1]

the lowest octane rating for New Zealand petrol is 91 then 95 then 98 and speacialist garages selling 102 (rocket fuel)but most sell 91,95 or 98

[Tamago]

here

ahh

and it's not E-85?

[frownonfun]

ahh

and it's not E-85?

i don't think so... goes 85, 87, 91 here. i seen some signs on a few pumps that mention the gasoline "may be up to 10% ethanol" but none specifically say E85 or anything.

[Tamago]

i don't think so... goes 85, 87, 91 here. i seen some signs on a few pumps that mention the gasoline "may be up to 10% ethanol" but none specifically say E85 or anything.

ok

interesting!

and no, 10% ethanol and E85 are not the same thing :)

[jambo101]

I was reading a Fit forum on FE when I read a post that was about how using higher octane gas could slowly wreck your motor over time by burning too hot and causing timing problems. .

Thats backwards ,,the higher octane burns cooler than lower octane thus the carbon builds up ultimately choking your engine and oil with carbon and sludge build up.You might want to check your timing for that rattling you are hearing as the car should run smooth and quiet on regular octane gas.

[Tamago]

Thats backwards ,,the higher octane burns cooler than lower octane thus the carbon builds up ultimately choking your engine and oil with carbon and sludge build up.You might want to check your timing for that rattling you are hearing as the car should run smooth and quiet on regular octane gas.

actually no.

higher octane fuel is less likely to detonate prematurely. this means it doesn't burn when it should without a timing/spark advance.

without a way to advance timing, higher octane fuel will cause your engine to run a little hotter (ever run a briggs and stratton on 93 octane? after awhile you'll notice the header will be glowing red hot)

[MUSKOKA800]

I would suggest that if your engine "rattles" on regular octane fuel then it has a problem that your selling dealer should have repaired (warranty?).
I'm no mechanic but can't imagine how different fuel could "fix" a valvetrain noise. But a KNOCK/pre-ignition yes. Improper ignition timing may cause pre-ignition which might be remedied by higher octane.
My question to the dealer would have been "why is the engine rattling?".

[Tonavi]

The dealer's service department that the noise(s) were nothing bad and that using better gas will quiet things down, but isn't necessarily better/worse for your engine.

I don't trust dealers 100% though, even though they should know.

[Tamago]

I don't trust dealers 100% though, even though they should know.

smart thinking, yeah dealerships, especially service writers, are generally poorly trained. more time is spent training them to "sell" than to "know" anything.

[shinlee]

In Odessa, the minimum is 86, and premium was 90, but here in austin, the minimum is 87, and high is 93

[jkuchta]

Higher octane fuel does not burn any hotter or cooler than lower octane. It is just more resistant to preignition and detonation. Running higher grade fuel will not do ANY harm to your engine.....driving like an old lady will do harm to your engine. Every now and then step on it and open the car up a little, and things will stay nice and clean.

Tomago, the Yaris is quite capable of adjusting timing to take advantage of higher grade fuel....and in response to your reply on the other thread....yes...my yaris does pat me on the back when I full up with premium:thumbup:

[Tonavi]

Has anyone noticed that sometimes (like today when it snowed), that the car feels extremely sluggish even when it shouldn't? Coming home from work today, I was checking if the parking brake was still on. The heat was extremely hot (over 170 degrees, normally it's 160), leading me to think it was running too warm. The radiator hose was rock hard with pressure.

Let it sit outside until about half an hour ago (zero degrees outside), and it started right up and drove 80+ mph without a problem at all.

Does your car ever have hiccups like this?

[silver_echo]

actually no.

higher octane fuel is less likely to detonate prematurely. this means it doesn't burn when it should without a timing/spark advance.

without a way to advance timing, higher octane fuel will cause your engine to run a little hotter (ever run a briggs and stratton on 93 octane? after awhile you'll notice the header will be glowing red hot)

i gotta try that... sounds kinda cool... but i will only try that on a lawnmower that i cannot fix otherwise...

The dealer's service department that the noise(s) were nothing bad and that using better gas will quiet things down, but isn't necessarily better/worse for your engine.

I don't trust dealers 100% though, even though they should know.

try a different toyota, or maybe a lexus dealer in your area... same motor company, and the techs get the same training... you are still under warranty, tell the dealer that there is an issue... if they will not listen to you, talk to toyota corporate... i had to do that because of my dealer trying to screw me on a recall after they screwed up my seat rails, saying that it was wear and tear... but whatever the service writer says, a sound like that is not normal from a motor with low(less that at least 80000 miles) and is not really common even then with proper maintenance... things like the dealer trying to make you wait out the warranty so that they can charge YOU instead of the factory warranty piss me off :mad:

[Tonavi]

without a way to advance timing, higher octane fuel will cause your engine to run a little hotter (ever run a briggs and stratton on 93 octane? after awhile you'll notice the header will be glowing red hot)

I can believe this, but going form 87 to 89 would wreck a motor? Using race gas, yes, using +2, though?

[360cubes]

[85]here

...and I thought everything was bigger (er, um, higher in this case) in Texas!

---------------------
Here goes:
Running higher octane fuel won't necessarily wreck an engine. Pump gas, generally no higher than 94 octane, is safe for use in all modern automobile engines. Knock sensors help compensate for pre-detonation, which isn't standard on all vehicles on the road. I ran 93 octane in my older (92 & 93) Dodge Spirit cars. Why? Because they saw a lot of mountain driving when I lived out west outside of Calgary and were gutless above 5000ft if I ran regular. At least with running higher octane fuel I can maintain speed going up hill with a few people in the car. The '92 was retired at 430,000miles (not KM), and the 93 was retired at 280K (miles) when I changed jobs and moved out east. I bought both vehicles used with 20-42K on the odometer. I ran service stations for several years by the way.

Keep in mind that Toyota tunes its V6 engines to run on 91 octane, even though the dealer will tell you that you can run 87 safely as the knock sensors will compensate. You'll also lose a few ponies this way. Some manufacturers post different HP numbers for this reason. A lot only post the maximum HP number for the sake of marketing with the fine print stating that you need 91 octane to get that HP number.

Running 100+octane tank after tank will cause damage to an engine that isn't specifically designed for it. Running E85 is for specific vehicles only as it contains 15% petrol and 85% ethanol (generally produced from corn/soybean). Regular pump gas can contain up to 10% ethanol. From all the fuel bills I've had delivered, not one stated that the ethanol content was above seven percent. The average is roughly 5% as that is what most vehicles can safely run on. Fuel manufacturers print off those "up to 10% ethanol" stickers strictly to make people feel better that they're helping the environment. Some older (80s, 90s) cars cannot run with more than 5% ethanol without gumming up engine components. Best thing to do in this case is read the owners manual.

My Dodge Durango R/T requires premium fuel from the factory as it has a performance PCM. When I fuel up my zero turn mower to make things easier on myself I occasionally use 91 octane for my small engines as well and they have given me no problems in the hundreds of hours I run them each season. If I need a high quantity of fuel for them I'll get 87 for the cost difference (10cents/L less).

I have something else for everyone to ponder (possible thread jack here). It was mentioned that occasionally, vehicles seem to have lost a bit of pep from one day to the next. Be it due to the temperature, weather, driver added passengers etc.
Well, I believe this: If you get a lot of moist air throughout the evening (heavy fog) and you come back later on that night after a drive, even if its short, a dry paper filter will collect some of that moisture and freeze overnight allowing less allowable air the engine is able to breath the following morning. This was actually a reported problem with Ford's latest 6.4L TD engine. The intake would fill with snow and debris causing a no-start condition! Lovely.

[Tonavi]

I ran some injector cleaner through the brake line, and there was some massive smoke action for almost a half hour! I work at a shop where we have an IV drip system for when we do fuel system cleanings, so I used that as it meters the cleaner (Valvoline synthetic fuel system...) and the air so the engine still runs somewhat smoothly. Two hours later, the shop is still foggy and has that sweet smell...

For 21,000 miles, it smoked like it had 100,000. The car rarely goes over 2500 rpm, so that means it's the ethanol in the gas that's causing most of the carbon. Note that the car runs like it's brand new, with an instant increase in performance!

[frownonfun]

found this article interesting and thought i'd share...

http://autos.aol.com/article/car-news/gasoline-octane/20090422002

[Yaris Hilton]

Running higher octane fuel than necessary will harm only your pocketbook. It doesn't burn more slowly, more coolly, more sootily, or in any other way differently after the flame front reaches it. The difference is that it's more resistant to autoigniting as it's heated and compressed by and ahead of the expanding burning gas. The unburned mixture in the corners of the combustion chamber that haven't yet been reached by the spreading flame front can spontaneously ignite en mass before the flame front gets there, going BANG! like a firecracker. That's the pinging or knocking we hear. If only a very small amount of gas is detonating, it makes a light rattle, while a larger explosion makes a louder knocking and puts more stress on the engine parts. Higher octane fuels either autoignite at higher temperatures, or they have to react longer at a given temperature and pressure before they go BANG!, so the flame front has enough time to get there and ignite the fuel mixture in an orderly fashion. But once the flame gets to them, they burn normally.

Very slight detonation won't hurt anything, and means that the engine is operating at maximum efficiency. Unfortunately, it's difficult to tell by listening whether you're in that optimum range or knocking too much and risking engine damage. That's why we have knock sensors that CAN tell the difference, and the engine control unit will retard the spark if it's getting excessive. Many engines will run more efficiently on higher octane fuel because the ECU will allow more spark advance when the knock sensor doesn't hear pinging. I've read assertions online that the Yaris' ECU will do this and give slightly more power and fuel mileage with higher octane ratings than the 87 pump octane gas. I don't doubt it, because I often hear that barely audible rattle with 87. But that's what it's designed and expected to run on, and it's what I'll keep running in mine. I don't expect enough benefit to be worth the price.

[Yaris Hilton]

BTW, try this experiment: Make an alcohol lamp with a small bottle with a hole in the lid and a piece of thick string fitting in the hole for a wick. Fill the lamp with denatured alcohol from the paint store, the kind that's ethanol with 5% or so of methanol in it (so they don't have to pay liquor taxes on it), not the kind that's mostly methanol with smaller amounts of ethanol, isopropanol and methyl isobutyl ketone. Or if you want to splurge, go to the liquor store and get some PGA, Pure Grain Alcohol. Light the lamp and pass a piece of cold metal back and forth through the flame to try to soot it up. You'll have a hard time getting any soot buildup from ethanol. Now do the same with a candle flame (paraffin wax is a mixture of hydrocarbons very similar to those in gasoline.) Big difference, huh? The "carbon" gunking up our engines with E10 fuel doesn't come from bad combustion of ethanol. It's from fuel additives, ironically mainly detergents, that are made for gasoline without ethanol and that precipitate more readily when ethanol is added to the mixture. The deposits peak at about 10% ethanol and decrease again as the concentration goes up. In port fuel injected engines, the biggest place this stuff ends up is in the intake ports and on the heads of the intake valves. Newer detergents like those in Chevron's Techron don't do this like the older ones. As ethanol-supplemented fuels become more and more widely used, refiners and distributors are going to have to switch to alcohol-compatible fuel additive packages.

[severous01]

wow, there's a LOT of seriously wrong info in this thread.

if you done your research, you know that higher octane DOES BURN SLOWER and is used in higher compression, more advanced timing applications for this reason....the spark is well before TDC for this reason, the fuel will start to burn well before TDC and then explode ATDC. higher performance engines REQUIRE this fuel because of advanced timing...and that's all you'll get with any of the aftermarket programmers....maybe a little fuel trim to enhance new timing. any way, the fuel is the same, and is actually has more addatives to make it lower octane vs higher...and lower octane fuel is cheaper than higher octane.

facts and myths: http://www.state.mn.us/mn/externalDocs/Commerce/Gasoline_Octane_Facts_102902052227_OctaneFacts.pdf

octane rating is the percentage of resistance to knock....yes, even tho they have 102 and 104+ or whatever. the higher the octane the more energy required to cause a burn or release of energy.

when an engine senses knock it fixes the problem by retarding timing. if you know anything about old school (distributor ignition) you know you can do A LOT with a simple twist of the Dist...2 or 3* can net you up to 20 hp in some cases (5.0 mustangs for instance) but at WOT you'll need high octane fuel...hence the retarding issue from the factory. efficiency.

the higher the compression, the higher the temps. higher temps inside means a higher chance of pre-ignition or knock...or ping...or whatever you want to call it. and since all engines now are computer controlled and most have knock sensors....the pcm would much rather save the engine by retarding and fuel efficiency than popping a hole in a piston cuz your dumbass decided to ignore it or keep goin cuz you 'had to'. any way, do some more research on wiki or the site i provided.

[newyar]

To the layman, all the complicated-sounding explanations of octane seem like voodoo. It's pretty basic though. The 3 common octane grades of 87, 89 and 92 are the exact same gasoline basically with the exception of retardants that are put in the gas to delay combustion of the fuel.

An engine compresses the gas/air mixture to a pre-designed amount, then at just the right moment (timing) the spark plug fires and ignites the gas. This is what pushes the piston down and provides the power for the engine. The more (higher) the compression, the bigger the bang. This is how high-performance engine designers increase the power output of their engines; with high compression pistons, rings, valves, etc. They have to be stronger grade components to handle the higher pressures, heat and shock of the explosion.

High compression and bigger bangs produce greater heat. Heat inside the compression chamber; especially if there's a bit of carbon that's glowing like a spark plug inside there can ignite the fuel before the plug fires... this produces what is known as knock or pinging. It robs an engine of power because the push by the piston is out of timing with when it's supposed to happen and the engine is now literally fighting against itself. Usually the fuel ignites just before the piston has reached the top of it's travel so it now has a downward explosion pushing against it while the piston rod is trying to push it UP and over top dead center (TDC) so it can travel downward like it's supposed to. It does go up and over but as you can imagine it's a shock to the engine and literally jolts it. Some of the explosion's power is wasted before the piston has passed TDC and this costs power. It can also literally wreck an engine.

In order to control this, retardants are added to the gas which is called the octane rating to DELAY the ignition sensitivity of the fuel. This makes it so that hotspots or hot combustion chambers in high compression engines won't pre-ignite the fuel because the retardant increases the temperature required for the fuel to ignite. In otherwords, only the spark plug now generates enough "fire" to ignite it. The higher the compression in the engine, the higher the octane rating needed to prevent pre-ignition.

People sometimes mistakenly think adding a higher octane gas will increase their power. But it isn't the gas that's producing the higher power, it's the higher compression ratio and design of the engine that's using the gas. 92 octane is the same gas as 87; the only difference is the amount of retardant in it to delay the gas igniting. Putting high octane fuel in an engine that isn't designed for it is not only a waste, it's actually not a good idea. If your engine is designed for 87, use 87. Putting in 92 will NOT increase the power, however it WILL increase the carbon build-up and deposits. The only time you might want to go up to 89 is if you live in an area that gets very hot in summer and your engine is running hotter as a result. If you experience pinging, loss of power in the summer when running the A/C and it's smoking hot outside, put some 89 octane in the gas tank. When the temps cool down go back to 87.

In a high compression engine, the heat inside the chamber is much higher than a normal compression engine so when the fuel ignites, it burns very nearly completely. A small amount of it however will not burn and it's that "residue" that appears on valves and heads as carbon build-up. The retardant in the gas that prevents knock also prevents all the fuel from burning; a necessary trade-off. This is why gas companies put detergents in their high octane fuel and advertise that fact; it's to help cleanse away the residue so it doesn't stick to the valves, etc.

If you put 92 octane in an engine that is designed for 87, you'll actually lose a bit of power because even less of the gas mixture inside the chamber burns than if it didn't have the extra retardant in the fuel. Same amount of gas was pulled into the chamber as 87, but less of it burned. The retardant SLOWS DOWN the burn so without the high temps of a high compression engine, it doesn't have enough time to burn completely before the piston is pushing the unburned fuel out the exhaust valve opening. Where does the unburned residue go? On your valves, heads, pistons and a bit of it makes it's way to your catalytic convertor. So yes if you've already reached the conclusion, high octane fuel in a low octane designed engine will actually muck it up over time so you'll need engine work sooner than if you had used 87 octane like the engine was designed for. Now the computer will read this and attempt to compensate by changing the timing but this is just that; <b>compensating</b> for a situation that's not intended.

So remember, 87, 89 and 92 octane gas is the EXACT SAME GAS with the exception of greater amounts of retardant in 89 and even greater amounts in 92. Unless you turbocharge or supercharge your engine, do yourself a favor and just run 87 octane like it was designed for. It's cheaper, burns more efficiently which means less carbon build-up, less emissions, more power. If your engine is knocking, pinging, rattling or making noises with 87 then it needs looking at and servicing. It's not the gas.

Sorry this explanation is so long; wasn't as "quick" as I'd intended it to be.

[chasd60]

I ran some injector cleaner through the brake line, and there was some massive smoke action for almost a half hour!

Is there something wrong with that statement?

[Ace]

I'm reading all this stuff about how people are wasting money buying above 87 octane gas but it's okay for high compression engine... okay so what is consider a high compression engine?... isn't most fuel efficient engine high compression now-a-day?

U.S. Yaris engine has a 10.5:1 compression ratio. Base on the info in this link
(http://www.imoc.co.uk/technical/article/octane.htm#q22), we should be using 100 RON octane. In America the service stations uses Pump Octane Number or PON, which converts to 95.8 octane (http://www.btinternet.com/~madmole/Reference/RONMONPON.html).

[Yaris Hilton]

wow, there's a LOT of seriously wrong info in this thread.

if you done your research, you know that higher octane DOES BURN SLOWER and is used in higher compression, more advanced timing applications for this reason....the spark is well before TDC for this reason, the fuel will start to burn well before TDC and then explode ATDC. higher performance engines REQUIRE this fuel because of advanced timing...and that's all you'll get with any of the aftermarket programmers....maybe a little fuel trim to enhance new timing. any way, the fuel is the same, and is actually has more addatives to make it lower octane vs higher...and lower octane fuel is cheaper than higher octane.
There is some wrong info (slower burning with higher octane) and some basic misunderstandings in your post. If you'll do your research, you'll find that what's slower about high octane fuel is the pre-flame phase of combustion during which the initial reactions leading to autoignition occur. The flame velocity and duration of the flame are not affected. The pre-flame reactions occur when the fuel is heated by compression, and by compression of the unignited part of the fuel-air mixture by the expanding ball of flame behind the spreading flame front. If you increased the compression ratio, at some point you'd have the fuel autoignite or detonate without any spark being fired at all, which is an upper limit on the compression ratio that can be used with a given fuel. Detonation that we're discussing is what occurs when the spark fires before any autoigniton occurs, but part of the charge autoignites before the flame front has spread through the whole combustion chamber.

In all engines, advanced timing is necessary because the flame front travels across the combustion chamber at a finite speed from the spark plug after it starts the fuel burning. The spark fires before top dead center, but full ignition of the charge occurs sometime after TDC. Most efficient conversion of the energy released by the burning fuel occurs when the fuel burns near the top of the power stroke, expanding more and therefore doing more work as the piston goes down. If the octane level is too low, detonation can be suppressed by delaying the spark so the piston is going down and relieving the pressure on the yet unignited part of the mixture so it doesn't autoignite before the flame front reaches it. As more of the fuel then burns at a larger combustion volume, the peak flame temperature may go down a bit but the engine actually runs hotter because more of the cylinder is exposed to the near-peak flame temperatures. The exhaust temperature will also rise, because the flaming gas has not cooled as much by expansion on the power stroke. A higher compression engine will need higher octane fuel to be able to use its optimum spark advance level and operate at maximum efficiency. Other factors like air intake temperature, combustion chamber surface temperatures and combustion chamber turbulence also affect octane requirements and optimum spark timing.

Preignition due to hot spots in the combustion chamber from carbon deposits and such is different from detonation, but detonation often causes hot spots to light up and cause preignition, and preignition often causes detonation.

Wikipedia has a good explanation of knocking here: http://en.wikipedia.org/wiki/Engine_knocking

That link to the state of Minnesota's "Octane Facts" is a good consumer-level explanation of fuel octane, that doesn't contradict anything I've said.

A very helpful, more technical reference is the Gasoline FAQ: http://www.faqs.org/faqs/autos/gasoline-faq/

There are many technical papers available online on fuel combustion that a bit of creative Googling will turn up. I've spent many hours reading quite a few of them. If you're really interested in the chemistry and dynamics of it, I'll recommend the seminal text Explosion and Combustion Processes in Gases, by Jost Croft, McGraw-Hill, 1946. (A translation of a German text that the U.S. government promulgated to advance aircraft engine and fuel technology at the end of WWII. I found a copy on eBay a few years ago.) Pretty much everything known about combustion in engines now is drawn from the information first assembled there, with refinements developed over six decades of further experimentation and improved sensing technology.

I'm not arguing to be argumentative. I'm just sharing information I've spent a lot of time and effort learning, and correcting a common misconception about burning speed being different as the octane level changes.

[newyar]

Lots of information; too much to read, including my own previous post. The short version? Unless you modify it with a turbo, supercharger, or something that changes the compression, use the octane rating recommended by the company that designed the motor. Going to a higher octane gas won't do anything for you other than cost more money.

[Ace]

Someone please show me where Toyota indicates that the U.S. Yaris or the NZ series engines were designed for 87-octane gas. Or that it runs better on 87-octane gas.

The Smart requires premium gas; Yaris has a higher compression engine.

[supmet]

^^ That little book that came in the glove box of your car - it's called an owner's manual. Crack it open sometime, or read more than the last post in this thread.

[Ace]

^^ That little book that came in the glove box of your car - it's called an owner's manual. Crack it open sometime, or read more than the last post in this thread.

Since you are so smart... please indicate the page on the manual or a link.

[supmet]

^^ 170 in my 07 manual

[Ace]

^^ 170 in my 07 manual

It said "minimum required."

Here, let me type slower.

Someone please show me where Toyota indicates that the U.S. Yaris or the NZ series engines were designed for 87-octane gas. Or that it runs better on 87-octane gas.

[frownonfun]

http://pressroom.toyota.com/pr/tms/toyota/document/2009Yaris_sfo.pdf

[Ace]

http://pressroom.toyota.com/pr/tms/toyota/document/2009Yaris_sfo.pdf

nice... and I can find a place where it say it's the minimum you should use.

[nemelek]

I am not sure if the elevetion that one lives at has a bearing on the fuel octane that can be used. I once had a 89 or 90 Nissan Sentra in which the owners manual suggested a higher octane at lower elevations. I always ran the cheap gas in Colorado with no problem. When I drove to California the car started to ping. Filling with a higher octane solved the problem while at the coast.

[frownonfun]

nice... and I can find a place where it say it's the minimum you should use.

well you asked to show you a place and i did... if still wanna continue to disregard this info that's really ok with me. i'm just gonna run the minimum or recommended because i certainly haven't seen any information supporting the use of a higher octane.

[Ace]

well you asked to show you a place and i did... if still wanna continue to disregard this info that's really ok with me. i'm just gonna run the minimum or recommended because i certainly haven't seen any information supporting the use of a higher octane.

Yes, you did. But the link is a press release (marketing) and not for the end user. The document that was given to me when I bought my Yaris states “Octane Rating 87 or higher” and not “87 octane is recommended”.

My point is if you going to say high octane for a Yaris is a waste of money then show me. I don't want to see some out dated article from before the days people bought 10.5:1 compression ratio engines off the car lot.

[frownonfun]

Yes, you did. But the link is a press release (marketing) and not for the end user. The document that was given to me when I bought my Yaris states “Octane Rating 87 or higher” and not “87 octane is recommended”.

My point is if you going to say high octane for a Yaris is a wastes of money then show me. I don't want to see some out dated article from before the days people bought 10.5:1 compression ratio engines off the car lot.

from what i am reading the engine has a high compression ratio, yes. but because of a delayed closing intake valve which lets air escape the cylinder freely rather than being compressed, the compression is reduced. this in order to make it more fuel efficient.

bottom line is the yaris was never intended for performance so there really is no reason to think that it would benefit from a higher octane. the whole purpose of the nz family of engines, i think, was for use with a hybrid electric motor. toyota's intent is to make the engine as fuel efficient as possible so i don't see any reason why a higher octane would be beneficial.

and yes you can find places where it states 87 is recommended and some places where it states it's the minimum but i think the fact that you can't really find any place that states higher octanes improve performance says a lot.

[newyar]

Geez what a series of posts. It says 87 octane is recommended because that's the octane rating the engine was designed to run on. The reason it says minimum required is because IF you need gas and 87 isn't available for whatever reason, you CAN run 89 or 92; it will run on it. However there's no benefit other than not running out of gas. It will not increase power, mileage or improve the performance above what 87 octane does. It will leave more carbon residue in the engine if you continuously run the higher octane for the reasons stated in mine and other's previous posts.

If you want to run the higher octane stuff... it's your car, your money...fill it up with what you want. Just don't be surprised if your engine gunks up sooner than everybody else's.

[newyar]

I am not sure if the elevetion that one lives at has a bearing on the fuel octane that can be used. I once had a 89 or 90 Nissan Sentra in which the owners manual suggested a higher octane at lower elevations. I always ran the cheap gas in Colorado with no problem. When I drove to California the car started to ping. Filling with a higher octane solved the problem while at the coast.

Altitude does affect engines. The air to fuel ratio does change between the thinned out air at high altitudes versus the denser air near sea level. However there's also a difference in gas quality; cheap gas at a cheap station may be truly cheap in every way. My Mazda RX8 does not like the cheap off-brand gas; I only put Shell in it. In a pinch I can use Chevron but it runs best with Shell. Tried some of the cheap off-brand stuff and the car ran like crap. Soon as I could I filled back up with Shell and the car was back to itself again.

The Yaris is more forgiving but I still put Shell regular in it. The few pennies you save in cheap gas you more than pay for later with repairs and having fuel injectors clog up, emission systems clog up, and engine gunk build-up.

[Ace]

It says 87 octane is recommended because that's the octane rating the engine was designed to run on.

Just don't be surprised if your engine gunks up sooner than everybody else's.

This is what I’m sick of. People assuming things that they have nothing to back it up with. I never say that higher octane is better for the yaris engine, just show me some proof that is not if you're going to make that claim. I did show where some would say it is better but did not state my opinion. If you’re going state your opinion then show me some facts.

I spent half my life working in the labs and offices of the world largest gasoline and oil companies here in Houston, would love to read some facts and not opinions.

[newyar]

This is what I’m sick of. People assuming things that they have nothing to back it up with. I never say that higher octane is better for the yaris engine, just show me some proof that is not if you're going to make that claim. I did show where some would say it is better but did not state my opinion. If you’re going state your opinion then show me some facts.

I spent half my life working in the labs and offices of the world largest gasoline and oil companies here in Houston, would love to read some facts and not opinions.

Well if you worked half your life in the labs and offices of the gas and oil companies as you claim then you wouldn't be asking for facts; you'd already know. How about you just contact Toyota, you know the people who DESIGNED THE ENGINE and ask them what they meant when they PUT IT IN THE MANUAL? Since you don't seem willing to accept the owner's manual as "facts" it won't matter what I or anyone else on this forum says.

Oh and keep in mind that the gas and oil companies WANT you spending more money on the higher octane fuels so they aren't about to tell you otherwise. Ask people who rebuild engines for a living; who service fuel and ignition systems; who make spark plugs, valves, rings, pistons. Ask the people who deal with the consequences of tens of thousands of miles of fuel usage in engines; they'll give you some "facts".

If you're "sick and tired" then relieve your symptoms by doing some research yourself instead of demanding others do it for you. I stated what I know based on decades of experience with cars. If you don't like it or disagree with it; fine. Everybody is entitled to their opinion. Why don't you just fill your tank with 87; run it out, measure your gas mileage. Then fill up with 92 and see if you can tell any difference other than the cost. If you can't, then there's your "facts". But it's your car; spend your money on whatever grade fuel you want to.

[Ace]

doing some research yourself... Everybody is entitled to their opinion.

Thank you for admitting that you have no proof and it’s just an opinion.

[keesue]

The Yaris was desgined to run on regular. Toyota states 87 octane as the minimun recommended fuel (nothing lower) in the owner's manual. Save the money for beverages and a turbo charger. :biggrin:

Toyota designed the car with computer controls to enable it to run a relatively high compression on 87 octane by dynamically retarding ignition timing based on feedback from the knock sensor; further, they designed variable valve timing to scavenge exhaust from the cylinders more efficiently at higher rpm, lowering cylinder temperatures for the incoming charge. Without this technology, the engine would require higher octane fuel to avoid fuel detonation. Temperature, the by-product of compression, is the determinate factor for octane. The higher the compression, the higher the temperature and the higher the octane requirement. By old school standards, the Yaris is a very sophisiticated little engine.

The Yaris' timing does not advance to account for higher octane fuel. Without higher compression, it would be pointless. It only retards from its set point to account for higher temperatures from engine load that would result in knock. The set point can be adjusted if this is out of spec or objectionable, but a little pinging under load especially in high ambient temperature is normal and is a sign that the engine is squeaking the last bit of energy out of the charge.

Unfortunately, the Yaris doesn't dynamically raise its compression ratio without the assistance of forced induction. Using a higher grade fuel isn't required. Without higher compression, higher octance fuel in and of itself, won't improve the Yaris' peformance or extend its mpg to justify the expense; but, if you want to spend the cash....:iono:

[BLAZINBLUEVITZ]

LOL at the constant argument between gas grades.......

[keesue]

Yeah, its fun. Kinda like the efficacy of 0-20 v. 5-20 and whether its recommended or not. Heh...

[1stToyota]

Someone please show me where Toyota indicates that the U.S. Yaris or the NZ series engines were designed for 87-octane gas. Or that it runs better on 87-octane gas.

The Smart requires premium gas; Yaris has a higher compression engine.

Simple. Factory tuning. Ever heard of canned tuners like Diablo, SuperChip...? Even they can be tuned for what octane you want to use. The Smart is tuned for premium and performance will fall off if lower octane is used, sort of like my GTO...I could get by on less than 91, but car was tuned for 91. Unlike the Smart, the Yaris isn't tuned for 91

And on page 384 ('08 manual) it says **87 octane or higher**
so I might try mid-grade for a while and see

[360cubes]

Just to note here that I operated and managed two service stations for six years. Companies advertise "may contain up to 10% ethanol" on the pumps to make you, the consumer feel better that you're somewhat helping the environment. However, go back a few years and millions of vehicles on the road can only run up to 5% ethanol content, safely.

Most loads of fuel that were delivered never contained more than 6% ethanol - ever. The most ethanol content was found during the winter months, to increase the freezing properties of the fuel (hence, "winter gas"). In the summer, ethanol content was around 4-5% average per load delivered. In reality, we have 'winter gas' all year round! It amazes me how people run out and buy gas line antifreeze bottles for $1/ea when even 2% ethanol content in the fuel means you'll still be able to start the vehicle in -40C weather without trouble. 5-6% means it'd have to be below 55C before you'd even think about having to add anything special to the tank.

E-85 is 85% ethanol, 15% petrol (gasoline) mix. This fuel is meant for E85 compatible engines only. It'll stall and gum up engines that aren't meant for this fuel.

As for the "87 octane or higher" label, this is meant to cover Toyota's rear end should you live in the mountains, for example. A difference in elevation (even as much as 2500ft above sea level) can lead to engine ping due to lack of oxygen, which will require you to run a higher octane. The engine will automatically compensate for the octane difference (hence, knock sensors). Knock sensors can only control the engine so much. If you drove 10,000ft up a long hill at a steady speed, chances are you'll notice engine pinging around 5,000ft if you had a tank of 87 octane.

Running a higher octane fuel on a regular basis won't harm the engine. On some low grounded areas you can find octane as low as 85 at the pump! Keep in mind the high-ish compression ratio of these cars at 10.5:1). Turbocharged or supercharged cars need not worry about elevation changes, due to the lower compression engines (8.5:1) and the need to run 91 octane fuel irregardless. You can run 87 octane fuel in a modern turbocharged vehicle, but performance will go down the tubes as the PCM is designed for it to operate most efficiently on 91 octane.

As mentioned, a tuner can be used to change the PCM mapping a bit if you wanted to run 91 octane on a regular basis...you might even gain 1hp out of the deal. If you were going to do a few engine modifications, a custom tune would be the way to go to better squeeze out every HP possible from your particular setup. Otherwise, just to tune an engine on 91 octane isn't worth while. Stick with what the factory said unless you live on a mountain top.

My '00 Durango R/T came from the factory to run on 91 octane. However, it doesn't have knock sensors and I cannot run a lower octane without severe ping even at part throttle. I've added performance mods to it anyway that require 91 octane, but if I had left it stock I'm sure I would've found a way for it to run on 87 like 01+ Durango models.