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Do you think it would be bad to put 110 octane gas in my mostly stock wrx? there's a gas station right by my house that sells it and before i got it i just wanted to make sure that i'm not shooting myself in the foot.
 

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A 1/4 tank will do ya. Don't run leaded gas with cats in your system. They will die a very quick death and you will be sorry.

The O2 sensors are much more tollerant of leaded gas and they don't cost that much. If you are going to play with leaded gas remove your cats and pick up an extra O2 sensor first just in case. Lots of guys have ran 10s of tanks of leaded race gas without having O2 sensor problems btw.

If the O2 sensor dies, your WRX will go into limp mode. You don't want to see what this is like if you have bigger injectors either.

Carlo
 

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if you can find 117 octane, the formula is 1 gallon 117 to 9 gallons of 93 and you get 100 octane gas.
if i only had 110 octane, use it 2 gallons 110 and 8 gallons 93.
ditch the cats, Carlo gave you good advice if you are going to do this
 

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I would be VERY surprised if you see any measurable performance improvement. Higher octane gas in a car that can't take advantage of it is wasted money at best, and can cause damage if it's leaded, as was previously pointed out.

A pretty well-informed guy wrote this FAQ about octane... :p
 

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you are correct, except that our cars with boost upgrades can see well over 300lb of cylinder pressure. these extremes love more octane as pinging causes much more damage under these conditions. and the article you quoted confirms this. better octane, less chance of pinging(detonation)
when we raise boost in an engine, the quality of fuel becomes a major issue very quickly.
Many WRX's that have been built(internally) for years will have the cat removed, run race gas, and make 70hp more.
this has been proven many times over.
ask any high horsepower b18c honda guy with a big turbo what happens when he increases octane.
I hope this helps.
 

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markmiller said:
you are correct, except that our cars with boost upgrades can see well over 300lb of cylinder pressure. these extremes love more octane as pinging causes much more damage under these conditions. and the article you quoted confirms this. better octane, less chance of pinging(detonation)
when we raise boost in an engine, the quality of fuel becomes a major issue very quickly.
Many WRX's that have been built(internally) for years will have the cat removed, run race gas, and make 70hp more.
this has been proven many times over.
ask any high horsepower b18c honda guy with a big turbo what happens when he increases octane.
I hope this helps.
That's why I double-checked to make sure we were talking about a "mostly stock WRX" before I referred him to the article I wrote. :p

Basically, it comes down to this:

Once you've found out how much knock resistance your engine needs, increasing the octane rating of the fuel beyond that point won't help you out.
 

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I agree, kind sir.
 

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since you're mostly stock, don't waste your money.

If you really want to use it, you're need to re-programm the ECU to advance the timing of the engine to take advantage of the higher octane, otherwise you won't get a complete burn of the air-fuel mixture, and eventually damaging the cats.
 
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