The last gas question

[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]

Originally Posted by Tonavi

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

[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]

Originally Posted by Tamago

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...

Originally Posted by 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.

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

[Tonavi]

Originally Posted by Tamago

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]

Originally Posted by frownonfun

[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-new...ne/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/externalDo...ctaneFacts.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]

Originally Posted by Tonavi

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/R...RONMONPON.html).

[Yaris Hilton]

Originally Posted by 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.

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.