I have searched the threads but could not get a clear answer. I work less than 1 mile from the VP race Fuel depot. I can buy VP 110 octane from the pump. Will this be to high of an octane for a 2004 JCW with no mods other than a CAI? I have to pick up C12 there today and need gas so I thought I would try some 110 octane if it should be ok. Any thoughts would be helpful.

 

That 110 may be leaded, which you Don't want to use, so be careful.

 

Never thought of that. It is leaded. Thank you for the input!

 

I've run 94 octane through my engine hoping that it would be cleaner, provide (a little) more power, and be a bit more efficient.

However after 4 tanks (1,500KM or 1,000 miles) my mileage suffered. I got about 150 fewer km on a tank gas, and didn't feel any more or less power output. Don't know what's up with that, so I switched back to 91 octane.

 

Thank you. I'm going to stick with the premium and not try anything new. The car has been running great so if it ain't broke don't fix it right?

 

So just some background info on the octane rating of fuel. Octane is a measure of a fuel's RESISTANCE to combust.. That is why higher compression cars and/or boosted cars need a higher octane. The higher octane allows the fuel/air mixture to be compressed without premature combustion, also called detention. You want the combustion to happen at TDC not before so you need the air/fuel to resist combustion until YOU want it to combust (i.e. spark).

So for your car with the mods it has only needs pump gas 91.

However, if you were to get a chip which bumps up your boost you would possibly need a higher octane. I would guess 93. Which you can make by mixing -

1.25 gallons of 100 unleaded with 3.75 gallons of 91. You net somewhere around 93.25.

There are chips and tuners that can make lots of horsepower on just pump gas 91 though.