isnt the lower the number the faster the gas burns ? and the higher the slower ? i heard this from my auto school .

 

Your suppose to use what ever your manual says. A 98 civic calls for 87 which will be fine. Octane numbers is just a anti-knock value It dosen't make your car run any better unless your running turbo!

 

I run 94 with my turbo.On a side note,My 89 Turbo caravan feels much better(at stock settings) with 94 instead of 89 oct. gas(as recommended).

 

remove your cat, and run 125 leaded.

 

I use 87 ARCO, and I am not kidding.

 

i got a 93 si and i use 91.

then again i have a b16a3.

in my old 94 ex coupe, 87 was fine and dandy for the d16z6.

late

 

True, I've always used 91. I'm sure it's a waste of money, but I just use it. I drive alot of highway miles.

 

Unless you advanced your timing, or your engine has high cylinder compression, or your engine is 'knocking' you don't need high octane fuel at all. There is absolutely no benefit in terms of power/reliability/fuel economy etc. The only difference is the higher resistance to detonation than 87-rated fuel. All the other additives (like detergents, anti-oxidants, rust-inhibitors, etc) are present in all fuel grades. Unless your manual says to use high octane fuel (because of the reasons mentioned above) you are just wasting money each time at the pump.