Now, the JK as we all know takes regular unleaded fuel (87 octane). If I were to put 89 octane, or lets say even 91, what affects does that have on the JK and it's engine?

I'm only asking because I'm going to be driving 800 miles within 24 hours and I'm curious to try supposedly better fuel.

Thanks!

 

Octane is actually a flame retardant. It stops the fuel from pre-maturely exploding in higher compression engines. If you do not have a high compression ratio you are just wasting money.

The only exception would be when people use power chips to re-program which messes with the ignition timing.

 

I have noticed some knocking running 87 octane at low RPM's, although its only minor pinging its there. I change up every other tank to 92 octane and the pinging went away. I feel some fuel is lower quality than others, i.e. a study of actual ethanol content. Although the pump claims up to 10%, it has been noted in some studies up to 20-25% ethanol. Just my two pennies.

 

It specificaly says in the manual that using higher octane than required may damage the engine.

 

I always run mid grade in all my vehicles and have never had any fuel related problems and I am a high mileage driver. Ive noticed better gas mileage and a (slight) smoother running engine in all my vehicles. My 2 cents.

 

Thanks for the help so far. Much appreciated.

 

No effect at all except a slightly lighter wallet.

Higher octane numbers do not mean higher power.

If your engine requires 87 octane even 110 octane av gas wont make it run any better.

And with computor controlled knock sensors you may get away with using 85 or 86 octane