What are the effects of premium fuel in regular fuel engine?

[kimokalihi]

I just filled up the metro last night and I pushed regular on the chevron pump and I guess maybe not hard enough or it's broken because it filled it with premium. That's the second time I've put premium in it but the first time was on purpose to see if there would be any difference in fuel economy. Didn't notice any difference.

What exactly does this do? I know octane cools the cylinder more to prevent detonation but what other effects (negative or positive) does it have aside from emptying your wallet quicker?

[gijonas]

I know octane cools the cylinder more to prevent detonation but what other effects (negative or positive) does it have aside from emptying your wallet quicker?

That is not what octane is.Octane isnt "stuff" its a rating.The octane rating refers to the volatility of the fuel,or its resistance to pre-ignition.Putting higher octane fuel in a car that doesnt need it wont hurt anything its just unnecessary is all.Your metros lack of turbo or high compression makes it unlkely to have any problems with lower octane fuel.

[kimokalihi]

I see that makes sense. Thanks

[Legacy777]

Actually.....putting higher octane fuel meant in a car meant for lower octane fuel can actually cause worse mileage and more wear on the ignition system. The higher octane fuels require more energy for them to ignite. This puts an added load on the ignition system. Most ignition systems....it shouldn't matter, but if you have a weak ignition system, it may give you issues....which may lead to lower fuel mileage.

However, if your ECU is programmed for higher octane fuel, it can raise timing, which will increase power and give you better fuel economy.

Also....just a note about octane. Isooctane is the basis of the 100 point octane rating scale. The higher the grade fuel, the more isooctane is found in the fuel. Octane is a hydrocarbon with lots of different isomers that are used in gasoline.

Wikipedia has some good info on it...

http://en.wikipedia.org/wiki/Octane
http://en.wikipedia.org/wiki/2,2,4-Trimethylpentane