Quote Originally Posted by chevelleman4292 View Post
matt is right (mopar) champion copper plugs ONLY every 30k miles.i have worked on dozens of newer jeeps and there really picky when it comes to plugs weather there worn out or a diffrent brand (like bosch platinum 2's they really don't like those),and atf+4 in the trans every 30k miles also.engine oil brand shouldn't matter as long as your using the right viscosity changing when you should and not using wallmart supertech oil lol. clean the throttle body also, old rag/tooth brush and small amount of carb cleaner it WILL make a diffrence.i have done all that and with 265/70/17's and a 3.7 still get 21mpg highway, 15 to 17 city.
I'm lucky to get 15, it's more like 13.5 average. I guess I should update this thread by saying that the "limp" feeling I was getting was caused (my guess) by crappy fuel. I have since stopped going to that gas station and have not felt the Jeep to be sluggish, it's not a race car but at least it feels like when I first drove it. I still have to replace the plugs and fluids, so I will report back on my findings after that happens.