Gasoline Type

[Snitty]

if it didn't do anything... then that means your engine was clean already

 

[joejeepny]

Jeep actually recommands 87 octane in the owners manual. I think you should use lower octane in short stroked engines and higher in a longer stroker. A short stroked engine like the 4.0 HO loves 87. A longer stroked 4.2 i bet would rather have the 89. The length of the burn time matches the stoke of the piston better providing fuel expansion through the hole stroke. If there is left over gas that isnt burnt when the valve opens unburned fuel is just wasted and dumped out the exhaust valve. On computer controlled vehichles you dont have much choice you have to use what doesnt ping but on older cars you can adjust timing for fuel savings and low octane or for power with preignition and high octane. It all depends on what engine, how its setup and what you want out of your vehichle.

 

[ahunt01]

RE: Sloppy steering

I never heard of that joejeepny. I thought 4.0 were actually happier with higher octane, atleast that's what I've read here. Jeep dealerships tell me the opposite.

 

[88Wrangles]

It also has a TON to due with the compression ration of the engine.

My Chevy with a pretty well built 454 will only run on 97 octane at the least, but does best with 110. Same with my dirtbike with a comp. ratio of about 12.? to 1....will only run on 110 and higher octane (really likes 120 though).

And my Jeep, with almost no compression (lets just say the engine was well worn) ran fine on 87.

 

[felix_santi]

I run the lowest octane gas and add some acetone to my tank. Runs like a champ.

 

[88Wrangles]

Good point! Acetone does work very well...even increasing fuel mileage!!