is premium fuel better/worse for a regular car?
October 27, 2009 in Other - Cars & Transportation
Did you know that you can save fuel and run your car on water
The Biologist asked:
my brother has started using premium fuel for his honda civic (which does not require premium), since doing so, his fuel efficiency has improved by 15%, I’ve heard some say that premium fuel for a regular engine is not good & vice versa, is it true?
Did you know that you can save fuel and run your car on water
Depends.
Engine compression dictates the octane needed. Too low an octane rating will cause pinging (predetonation) and eventually destroy an engine. Too high an octane rating is wasted as heat in the exhaust manifolds.
Premium (91 octane) is needed only for performance motors, and some luxury vehicles; there should be no difference in the mpg when using a higher octane rather than the recommended 87 octane…why spend the extra $$
An engine that does not require premium fuel gains almost nothing by using it. If your brother is getting better gas mileage it is because he is hypermiling which means driving for best mileage. He may not even realize he is doing it but he really wants to believe in the premium fuel idea and subconsciously accelerates more gently, anticipates reasons to coast and slow,drives slower, etc. Using premium fuel won’t hurt the car, but it will cost more per mile to drive. Even using regular in cars requiring premium won’t generally harm the engine as long as it doesn’t ping or knock when using it.
The owners manual for any car gives the recommended octane level for the car. Running a higher octane is only good to clean the system out once and a while. One tank every couple months is all you need to do that.
Fuel burns heating up air which in turn pushes the piston. Low quality low octane fuel and air mixture detonates it pings and knocks. The knock might not even be audible high frequency and to fast to notice but a knock sensor hears that noise and retards the spark timing to limit spark knock ping. That cuts down the gas mileage. running high octane in a regular gas motor will not hurt the motor it just might not have enough compression pressure to use all of the fuel each intake, compression, power, exhaust cycle. I doubt that a car that got 32 miles a gallon on regular could improve as much as 15% on premium fuel. But just 2 or 3 more miles a gallon is all it takes over a 13 to 20 gallon tank to make the extra cost of better gasoline even out. It is best that you look at the gas filler door and consult your owners hand book before choosing what fuel you want to use. Both of my cars say “premium fuel recommended” on the fuel doors and in the owners manuals
in a honda civic, don’t use premium fuel. there are ZERO benefits for you. its a waste of money. it doesn’t improve mileage, he’s probably just imagining it. only use premium in engines with high compression. if you put a turbo on your civic, then you’d need premium. other than that, just use regular. and yes you can use regular if you have premium fuel in the tank if you were wondering.