Si and Regular Unleaded

[sjuergens88]

first off i am not an Si owner, and i know that you are supposed to run premium, but why cant you just run regular unleaded?

[mycvksi]

your engine will knock and your car will hate you, i don't know exactly because i've never done it but iv heard

[vtak07]

lol i thought about this last night when i was filling my car up and the price was 4.04 a gallon.

[Tredd]

im pretty sure it has to do with our K20 engine having a higher compression ratio or something which is what gives our 4cylinder engines more power than most 4cylinders. My friend told me about it but i forgot the specifics.

[nachobel]

K20z3 11:1 compression ratio. throw low octane gas in there and rev to limit (well, you can't lol, car says NO) and engine knock will destroy your engine, except the sensors detect it and retard the timing, which gives you horrid performance and bad gas milage.

so, you could do it, but it'd be dumb.

[tite681]

Pay the extra for premium. It makes up in the gas mileage. Yeah, I've tried both.

[FGJake]

I didn't even know that the Si required premium fuel when I first got it (didn't notice the sticker on the inside of the fuel door ) and ran regular fuel for about 6 weeks until I realized that my engine hated me. It started knocking and I immediately cleaned my injectors and switched to premium.

[Bertelicious]

A family member inadvertantly put regular in my car and when I got back from vacation the car was running like shit. I asked who put gas in my car and what kind, they told me. I was pissed but nothing I could do at that point. Went easy on the motor for the last couple gallons and even then the motor hated it. DONT DO IT IF AT ALL POSSIBLE.

[Firestrife]

what they all said is right, some will say that its fine but your gas mileage goes down and the engine has to cut back a lot giving you crappy performance and lower overall output. In the long term it can also destroy your engine in the right situation.

[Dar-Dar]

putting regular fuel to a Civic Si is like feeding catfood to a dog.

[Si 07]

Originally Posted by Dar-Dar

putting regular fuel to a Civic Si is like feeding cat food to a dog.

how about

unfiltered water

and expensive

bottled water

lol

[NittanySi]

i use regular unleaded since gas has been so expensive, haven't noticed much of a change, if any, between performance and mpgs. Still getting around 27mpg/tank.

[ryker]

Heat is the reason for high octane fuel. High compression heats up the combustion chamber, piston top, and head area. The spark plug tip gets soo hot that it becomes an source of auto ignition. The fuel pre-ignites thus knocking sound.

Some people living in cooler location might be able to get away with low octane fuel. As summer temps climb those using regular gas will notice knocking, pinging, and bad MPG.

Yes gas prices are high. But the cost from regular and high octane has always been and will almost always be the same .30-40 cents higher.

If you really want to be cheap try using a colder heat range spark plug. This will allow you to use low octane gas.

[Doeboy211]

4.25 here a gallon of premium in nyc, I think im gonna buy a bike soon, and im a lazy mofo!

[tite681]

Originally Posted by FGJake

I didn't even know that the Si required premium fuel when I first got it (didn't notice the sticker on the inside of the fuel door )

.
I didn't see the sticker either. The salesman at the dealership told me I can use regular unleaded so it's not like I was looking for a warning sticker. Only lasted 1500 miles. I was getting about 21/22 mpg.

[solidust]

geeze arent there like a million threads on this?

[orbhot]

Originally Posted by ryker

Heat is the reason for high octane fuel. High compression heats up the combustion chamber, piston top, and head area. The spark plug tip gets soo hot that it becomes an source of auto ignition. The fuel pre-ignites thus knocking sound.

Some people living in cooler location might be able to get away with low octane fuel. As summer temps climb those using regular gas will notice knocking, pinging, and bad MPG.

Yes gas prices are high. But the cost from regular and high octane has always been and will almost always be the same .30-40 cents higher.

If you really want to be cheap try using a colder heat range spark plug. This will allow you to use low octane gas.

Why then do some, if not most sport bikes (which have even higher compression) only require regular? They must use colder plugs?

[cderalow]

how many f-ing times can this be asked?

[liquidr1]

Originally Posted by orbhot

Why then do some, if not most sport bikes (which have even higher compression) only require regular? They must use colder plugs?

Um, modern sportbikes do require premium.

[SiCivic83]

First thing I noticed about this car before I got it was that it was premium only. That's the only thing I run it with.