What octane gas is required / recommended for the Del Sol Si and VTECs? I know the S drinks 87 like a normal base Civic, but I was wondering how much a VTEC would change my fuel costs from a Civic DX...

 

87 for Si, 91 and up for VTEC. You only need higher octane fuels for motors with over 10 points of compression, and FI, obviously.

 

91 octane. whats up with that? "regular" is 87 "plus" is 89 and "premium" is 93, was it ever diffrent? it just seems a weird number to choose. maybe overseas they pump diffrent octanes? :dunno:

i just use premium always, the mileage is so good that i only have to fill up once or twice a week, and its only like $16 to fill it.

 

91 seems to be a popular required octane for some reason... I notice quite a lot when reading Road and Track that high end cars require it and then I go to the station and see 87, 89, and 93, as you mentioned... I only see 91 as often as I see 94. Even the Ferrari 360 only requires 91 so I have NO idea why 93 is offerred...

 

i guess its better to have higher quality fuel than nessary than a lower one.

 

A higher octane rating indicates a fuel's ability to retard detonation; intrinsic to this ability is lower combustibility (which is why racing fuels are oxygenated); so in effect, a car with say 9 points of compression will make less power with 91 rated than it will with 87, simply due to the nature of the fuel. I can think of a lot of ways to better waste money.

 

but what about 10 points?

 

A 10:1 car will make more power with 91 than a 9:1 will with 87. The 10:1 would probably make even more with 87... but at the same time it would be damaging itself with premature detonation. I could be wrong about the more power aspect, but I know that more power lies with higher compression and octane.

HOWEVER all the Honda VTEC engines use their knock sensors to set their timing agression. If you put 93 octane in any VTEC engine the car will be faster than with 91, after a short period for the ECU to realize that it's been fed 93. This even applies to the Odyssey.

 

Where do all you people live to find 87, 89, and 93 at your stations? Here in Cali all I ever see is 87, 89, and 91. Some stations omit the 89.

 

CT and NY