going from 91 to 87 gave me CEL! FLAME ON

[enviri]

i've been driving my yaris ever since i got out of the lot with 91 (93 when possible) and never gave it any thought....now since read the forums, i might as well give it a try, so basically i had 2 tanks of sunoco 87 (loong drive today, CT to ME and back, family thing) and on the 2nd tank, after the fillup, CEL showed up! I wonder if this will go away for the car to readjust timing, since its the first time the car had a tank of only lower octane lol...first tank didnt count since it was 91/87 inside. what do you think? btw im ordering a scangauge tommorow.

[supmet]

Need to know the CEL code(not tightening the gas cap can throw a CEL) You can go down to auto zone(don't know if they're east coast but I'm sure there's a part store equivalent) and use their tester for free while you're waiting on the scangauge.

[enviri]

i double checked the gas cap, and took off the neg terminal overnight and see what happens.

[The little red pill]

that's what you get for using 87 octane. Not only do I use 93, but I add octane booster to give me about 97 octane. I even have a NOS sticker on my car to prove how cool I am!

Seriously though, most likely the gas cap! I had it happen to me on a different car. I actually had to get a new gas cap, because the rubber gasket on mine was bad.

[CtrlAltDefeat]

87 wont give you a CEL unless there was water in the fuel. the owner's manual even tells you to use 87 octane. you're wasting your money for nothing

my 08 manual says 87(research 91)

[CtrlAltDefeat]

looking at it now, my 2008 Owner's Manual says on page 347: "Unleaded gasoline with an octane rating of 87 (Research Octane Number 91) or higher.

[CtrlAltDefeat]

I just wonder what "research number 91" means... sounds like 91 preferred, but it will run on 87...

[CtrlAltDefeat]

:iono: dunno... doesn't really make sense for them to tell you to research the less preferred rating when 87 is common and cheapest...

[Kaotic Lazagna]

Cheapo gas? I go from premium to regular (premium at least once a month), and I never had a CEL come on. I only use Chevron as well.

[IllusionX]

guys guys guys... RON91 = PON87

in Europe, they use Research Octane Number, while in NA, we use Pump Octane Number. That's why you see 100+ octane numbers in Europe. Their gas is no different than ours. hehe.

[ROCKLAND TOYOTA]

GREAT, another gas subject that will bring out all the experts. how about giving us that code you threw so we can see whats up......

[Tamago]

GREAT, another gas subject that will bring out all the experts. how about giving us that code you threw so we can see whats up......

he reset his ECU before checking it.

:laugh:

FAIL

[Tamago]

that i didnt know thanks for the info the RON PON one

ours is actually referred to as (RM)/2

[IllusionX]

ours is actually referred to as (RM)/2

It's actually (R+M)/2. (RON + MON)/2.

anyways, wikipedia is a good read.
http://en.wikipedia.org/wiki/Octane_rating

[mikenacarato]

that's what you get for using 87 octane. Not only do I use 93, but I add octane booster to give me about 97 octane. I even have a NOS sticker on my car to prove how cool I am!

Seriously though, most likely the gas cap! I had it happen to me on a different car. I actually had to get a new gas cap, because the rubber gasket on mine was bad.

you know you will foul your plugs out right? octane increased additives will burn them up. if you have been doing it for a few tanks, pull a plug and see if its turning an orangy burnt color. your eating away the electrodes.

[IllusionX]

you know you will foul your plugs out right? octane increased additives will burn them up. if you have been doing it for a few tanks, pull a plug and see if its turning an orangy burnt color. your eating away the electrodes.

As is, higher octane will not do any harm, nor give better performance/mileage.

The only thing is that SOME companies put cleaning additive to their premium fuel. If the engine is not knocking, there's no reason to put higher octane fuel.

/end of discussion.

[mikenacarato]

your wrong, why do you think we cant put race fuel in our cars for extended periods of time...it will burn them up because they will run too hot.

[Kal-El]

Why do some of you insist on using high octane? The Yaris was designed and calibrated to run on regular 87. Using premium may do the same type of long term harm as using regular in a car that requires premium.

And why waste the money?

[Tamago]

Why do some of you insist on using high octane? The Yaris was designed and calibrated to run on regular 87. Using premium may do the same type of long term harm as using regular in a car that requires premium.

And why waste the money?

you don't really understand petrol do you :confused:

[mikenacarato]

premium in any car wont hurt, using a too low octane rating will cause pinging.

[Yaris Hilton]

Octane boosters containing MMT may cause your catalysts to fail prematurely, and can clog them up severely so the engine can't breathe. That reddish stuff you see on the plugs is manganese oxide, and it's a lot worse on the catalyst than on the plugs.

[07WYarisRS]

your wrong, why do you think we cant put race fuel in our cars for extended periods of time...it will burn them up because they will run too hot.


race fuel does not burn hotter
race fuel in a regular engine will make less hp and run cooler. the flash point is to high and the engine will not burn it efficiently

[1stToyota]

premium in any car wont hurt, using a too low octane rating will cause pinging.

There are TSBs out there for using premium in cars that are tuned for 87 octane; Lincoln for example...causes excessive cranking times.

[ROCKLAND TOYOTA]

There are TSBs out there for using premium in cars that are tuned for 87 octane; Lincoln for example...causes excessive cranking times.

:iono: always gotta through that domestic car knowledge in there.....

[mchllp925]

Just something I found on the net.
Whether you believe this or not, it may help with this debate on octane.:iono::smile:


Octane levels rate the different types of gasoline available. The number signifies the burning properties the fuel will produce when it reaches your engine
. The standard octanes are 87, 89 and 91. The higher the octane rating the cleaner the fuel burns in your engine. Because of the clarity of the fuel, those with higher octane levels burn faster.

For cost effectiveness when gas prices are high, even if you normally use a higher octane, you can safely run your car on 87 octane and see no ill effects. In most cars performance won’t diminish. However, when used on a regular basis, over time there will be some amount of buildup in your fuel injectors. Because it is the lowest grade of fuel, manufacturers have designed all their vehicles to run on 87 octane. Auto makers will recommend that you use premium or supreme in some cars; but realistically the system is designed to run solely on 87 octane.




Both 89 and 91 octanes are faster, cleaner burning fuels that will help reduce and eliminate buildup on your fuel injection system. If you do a considerable amount of driving it would be wise to consider using these on a regular basis, because of the wear and tear to which your engine is exposed. High performance vehicles should be run on higher octane fuel to help keep the engine running in top condition. For example, you can safely run 87 octane in a Ford Escort for the life of the car and not really see any difference. However, if you usually drive a Chevy Corvette, 91 octane will be beneficial to you and the car. It’s safe to say that if you’ve spent that much money on a car you’re going to do everything you can to keep it in tip top shape.

What’s the safe grade for your car? If you do an average amount of driving; meaning you put the normal ten to fifteen thousand miles on your car each year, 87 octane will be fine. As a preventative measure, it’s a good idea to fill up with 89 or 91 octane once in a while. Once a month should be just fine and will accomplish a good cleaning of the fuel injectors in your vehicle. Any buildup will be removed and you may notice a change in performance and fuel economy as well. A good fuel injector cleaner or gas additive will do the same thing. Ask your local auto supply or mechanic to recommend one that suits your car and the performance you’ll want to get out of the treatment. If you choose the additive route, you’ll want to include it once a month as well just as you would a tank of high-octane gasoline.


For people who normally put substantial miles on their vehicle each year whether for work or otherwise, higher octanes will be beneficial to your vehicle. Just as oil changes extend the life of your motor, higher octane fuels help the engine to run smoother and reduce the wear and tear on the motor considerably in vehicles that are used a lot. Buildup from low octane reduces your fuel economy and makes the engine have to work that much harder to accommodate your driving needs.


The owner’s manual for your vehicle will provide the recommendations for your car. If there are any certain guidelines they provide you can follow those as well. Being that your car is the second biggest investment in your life, it’s best to listen to the manufacturer’s recommendations.

[Bob Dog]

I've alomst 25,000 miles over the past two years with never anything but 87 octane. Likely you came across a gas station ( you said you were on a long drive) , other than one of your usual ones, that had contamination in the fuel.

[DerFlosser]

These threads are getting old.....why would somebody buy an econoncar designed to run on 87 and put in 91 or 93? It's counter-productive and counterintuitive. The car is designed to run on economy fuel. Now...for the question at the top of the thread...likely a coincidence that you have a CEL after changing fuel grade(s).

[1stToyota]

:iono: always gotta through that domestic car knowledge in there.....

He said premium in any car :iono:

[1stToyota]

These threads are getting old.....why would somebody buy an econoncar designed to run on 87 and put in 91 or 93? It's counter-productive and counterintuitive. The car is designed to run on economy fuel. Now...for the question at the top of the thread...likely a coincidence that you have a CEL after changing fuel grade(s).

:thumbsup:

Yeah, I filled up 2 times in a row with mid-grade, funny, first time I've ever noticed a rough idle. :thumbdown: