Mid-grade fuels (89 octane) are made (genericaly speaking) using one part premium and two parts regular. The price is generally right in the middle between premium and unleaded. You're paying for 50/50 but getting 33/66. A friend who worked for Mobil told me that mid-grades are basically a marketing scam. Consumers who don't want to pay for premium buy mid-grades. No real performance increase, but a nice margin boost for the oil company.

I did my little premium experiment and my 07 EX actually prefers regular 87 octane. Idle was a little rough with premium and the mileage was about the same. My car is not very fast (like most un-modded Civics). I bought it for the mileage. If there was any performance increase, I didn't notice.

 

I only pump Premium on My 2000 Si. I cant run other fuel....... just premium.

 

94 or higher

 

Yes, it helps, for YOUR SITUATION. Absolutely no d-series Civics should be running anything other than regular 87octane unless you're running Nitrous, Turbo, Supercharger, or aftermarket internals that raise compressoin, PERIOD.

No, it does not help your stock or mildly modded civic

 

correct me if im wrong, but in the civic ex owners manual it actually says that there is no benefit to using higher octane than 87 and you will see no performance increase. i have to buy 92 or higher though because of the turbo....it sucks

 

i run on 98 octane. we dont have anything below 95 over here (uk)

 

Mmmm.. I know my grandpa's 2006 Civic Si says it should only run on 93 octane gas. I really don't see why it matters. But.. *shrugs*

I always get 89 octane. But with gas prices at 2.98 in Illinois, its such a hassle.. I rememeber when it was 2.50 or around there, and i'd always be at 1/4 tank of gas, and I would put 20 bucks in it about every two weeks, and that 20 bucks will fill me right all the way to full. It was nice. But now, since prices are an average of $3.00 it usually only gets me 3/4 full from a 1/4 tank.

 

06 Si needs 93 because the k20 has high compression.

 

the lower the octane the more power you will make but fight detonation more, higher the octane the less power you will make and less detonation you will make

 

the 00 Si has also high compression. Myfriends dad has his own Honda shop and he told me to just run Premium.