kovacsr15

my stock 4.6 requires regular gas .will it run better on 93 octane not sure it will cause any probems in the long run.

DRAGUL

It is a waste of money if your car is not tuned for it.

audioAl

Try it and see, my 3.7 has variable camshaft timing and can tell if I'm using 93 octane.

cliffyk

No without a tune it will not "run better", nor will it cause any problems except making your wallet lighter as was mentioned above...

WJL

Is this because the timing needs to be advanced to take advantage of the higher octane or is it because the fuel injection system will limit the amount of fuel allowed anyhow, or am i completely in left field all by myself?

Stevo86

It's the timing. Advancing the timing allows the engine a few more moments to burn all the fuel in the cylinder but if the fuel achieves combustion too early you get spark knock. This is why you use a higher octane fuel which is basically harder to burn in performance applications.

Believe it or not because 93 octane is harder to burn than 87 you can actually do yourself a disservice by using it if your car isn't tuned for it.

71_340

Waste of money! The exception would be if you find premium without ethanol, you might get a little better fuel mileage; but then you pay more for it.

cliffyk

The stock 2V tune, devised to allow the engine to run on 87 octane fuel, and not damage itself in the process, sucks--big time. You can read more about that and recommended mods here..

Short answer though, generally ignition timing can be/is advanced when running higher octane fuels.

It is a common misconception that higher octane gasolInes are "harder to burn", they are not. Other than that one would be throwing money away using premium fuel in an engine that does not need it there is no downside--as has been stated above there is no upside either.

Their advantage lies solely in increased resistance to detonation--more about octane here...

WJL

That's great stuff, now i want a new plenum.