I have a '96 Civic Ex with a little over 180k miles on it. Performance-wise, it only has a cold air intake and a cat-back exhaust system. The previous owner has always ran the car on unleaded, 87-octane gas. I have a few buddies with olderCivics that say they have noticed better gas mileage and less engine noise from using mid-grade, 89-octane gas. Basically my question is should i run out my 87 and ifll the tank wit 89, or is it not even worth the extra 10 cents per gallon?

 

The lower the octane gas the better fuel economy you are going to get but the more risk of detonation occurs. Really the only reason to run higher octane gas is if your engine knocks and pings with lower octane gas which older cars will do or your are running forced induction like a turbo or supercharger.

 

So basically you're saying i should stick to 87? The engine doesn't ping or knock or anything. Really, it doesn't make many wierd noises besides a whirringsound, which i have been told is the belt.