I think my GC needs new spark plugs. It's about to turn 90K and I have not put plugs in since I bought it 3yrs ago with 60K and it's idling a little rough.

The manual calls for the old style Champion Copper Plus single electrode plug (rc12mcc4). Since mine is not a HO motor and is the flex (E85) model I was wondering if you've had a better experience using a different or "hotter" plug. I get good mileage as it is now, some times as much as 24MPG depending on conditions. Performance seems like it always has, pretty good.

I appreciate your input based on your experience with this engine.

 

That is the plug the manual calls for. At 24mpg, I see no benefit to using anything else.

 

Put the Champions in today. Runs a lot smoother, didn't affect gas mileage at all. This is my first WK and E85 flex motor, sure seems odd that this system requires so much more care & feeding than the WJ and XJ's I've owned but uses old school copper spark plugs.