Please help: is premium fuel necessary?

I am about to buy a 2002 JGC Overland. I notice that the vehicle says "premium fuel RECOMMENDED." To me, recommended and required are 2 different things. Do you know if running regular gas will harm the engine or will the performance just be hindered? All I know is that the H.O. engine has a higher compression ratio, but it does not have an advance spark timing like the 5.9 did, and that one required premium. Thanks.

mcs219

The higher octane of the premium fuel slows down the burn rate of the gas. It will have less tendency to pre-ignite or ping as it is sometimes refered to.

The pre-ignition can damage the pistons, rings and bearings over time.

Where it says recommended, I would definatly fill with premium from an empty tank and at other times to bring up the octane level if I chose to go with regular on a part tank fill up occasionally.

If you pull a trailer or travel with a full load in hill country - definitly use premium

Recommend you talk to the lead technician at the dealership and see what he says too.

JD

I believe you can use regular but you will also loose some performance.The knock sensor should automatically retard your timing to compensate for the lower octane but with this you also loose performance and fuel milage. You would be better off using premium as you will have better all around performance and better fuel milage. I think this is why you see some people getting worse MPG,they use cheaper fuel. I only use premium in both of our GC one I6 one V8.