very basic question

I just purchased a 2001 g20 a few months ago, but i've only been driving it recently. what kind of gasoline do you use? i've been using just regular unleaded, but would it be better to use midgrade? i've heard that using midgrade for some cars (i.e. suvs) actually decreases your gas mileage.
thanks
emily

You will notice a benefit in performance & drivability with the higher the octane fuel & slightly better economy per mile (but the fuel is normally more expensive in the first place)

Unless you have advanced your timing, I would run 87 octane. Use the money saved towards mods. :D

i use between 87 and 89 at major brand stations only. works okay so far. :p

actually, you wont notice ANY increase in performance OR gas milage by using a higher gas grade in the G20 (unless you are advancing your timing for performance, which would require better fuel).

higher octane gasoline is more resistant to combustion. since combustion is a slow process (it takes up to 60 times longer than an explosion), it's quite possible that you wont end up burning every drop of fuel if you put premium into an engine that is tuned for 87. that may be what you heard about decreased performance with higher octanes. then again, it would probably be so subtle you wouldnt notice.


i havent confirmed that you can lose performance by using a higher than necessary grade of gasoline, but i have confirmed that it does not... COULD NOT... help either gas milage or performance. keep in mind that all the additives they put in premium, they put in plus and regular, too.

even if you dont agree with the above statement, you would have to be a FOOL to believe that putting premium gas will improve the gas milage of your car to the point where it offsets the extra cost.

i'd say that's just my $0.02... but it isnt - those are facts.

Originally posted by Brian P
higher octane gasoline is more resistant to combustion.

Actually, it's more resistant to auto-ignition.

Got everything else exactly right.

I stand corrected,but here in the UK there is a noticable difference
between standard unleaded fuel & Super unleaded.
I believe that Subaru even recommend the higher octane here for that very reason,my brother has a Prodrive Imprezza & the dyno showed
approx 5-7 bhp increase with the super unleaded !
So I guess its a case of try it & see

Originally posted by nismo_gt
I stand corrected,but here in the UK there is a noticable difference
between standard unleaded fuel & Super unleaded.
I believe that Subaru even recommend the higher octane here for that very reason,my brother has a Prodrive Imprezza & the dyno showed
approx 5-7 bhp increase with the super unleaded !
So I guess its a case of try it & see

Yes, that is because the Imprezza is tuned for the higher octane. When you run the lower grade petrol, the knock the ECU reads the engine knock and retards the timing, keeping the engine from blowing up and also reducing the power.

If someone builds and tunes an SR20 for higher octane petrol, such as running a JWT ECU, you can run lower octane, but the ECU will pull out timing from the ignition map and you will make less power.

It's not the petrol that is making the power, but the tuning to take advantage of the higher octane.