I have an 02 1.8t quattro and i recently went to a full service station where the employee put in 87octane instead of 93. My car requires 91 octane and i was curious what the outcomes are for putting in the wrong type of gas. I have about half a tank left and i want to go buy premium and fill up the rest of my tank to lower the concentration of 87. Is that a good idea? Can anything bad really happen from using the wrong octane? Write back with some constructive criticism =]

Thanks

 

Basically your engine will adjust for it. The ECM will retard the timing of the engine for the lower quality gas. Youll only notice sub-par performance, maybe alittle knock/ping. It should'nt throw any CEL codes or anything like that. I would go put the 93 octane in over that 87 though, that might be a good idea.

 

yeah get some better gas in there... you can run on 87... its just not recommended.

 

Your engine will not implode at least, so don't worry bout it, one time of low octane is completely harmless. Did you at least get free gas out of this?

 

The same thing happened to me once. My '04 did get the CEL. It was still under warranty, so i took it to the dealership. They told me that a check valve (i think thats what they said) had to be replaced in the fuel system. Of course, I didn't volunteer that the wrong octance gas had been run, but they did ask we what grade of fuel i use.

 

No worries, just dont push it hard, when your tank is half empty or so, try to mix it with premium.

 

thanks guys i think im going to go get some 93 and create a mixture lol

Could the lower octane mess with the spark plugs or the maf?

 

Not from one tank

 

I'd guess that since someone filled your tank your in NJ?

Its cold in NJ, you could probably run 87 all winter long and never notice a difference.

All octane does it reduce pre-detonation or the fuel igniting due to heat in the cylinder before the spark plug fires.

The colder the air/weather the less the need for octane.

That is the only difference in the fuel. If you had any failed part due to putting in 87 it was just dumb luck, the fuels are the same except for their volatility rating.

If the car has a knock sensor it'll detect pre-detonation and pull timing which will reduce heat in the cylinder and get you away from it.

GM ECU's if they detect knock in a engine they will pull timing all the time until you refill the gas tank.

Cut way down on warranty issues for 1 single bad tank of gas and knock issues.

 

I have a 2004 A4, 1.8T A/T and I have put 87 octane in the car since I got it new in Oct, '04. I just turned 45,000 miles on it and, other than the performance issue, I've had no bad effects from uing the lower grade gas.

I have read a couple articles that compare the MPG of the 87 octane vs the 91 octane and they indicated that, over a long period of time, you probably end up paying about the same, based on cost per mile/MPG.

So, if I had read those articles 5 yrs ago, I probably would not have used the lower octane rated gas.