Dear Tom & Ray: I have 2004 Jeep Grand Cherokee Limited with the 4.7 V8(235HP) with the Quadra Trac 4 WD and only 54000 miles. It’s a fully loaded, super clean & wonderful car. The EPA MPG is 15 city and 19 highway and it really lives up to the claim. I average 13.8 city and 19.5 highway(with a good tail wind) and am a very careful driver…easy on the gas, proper maintenance, etc. In a desperate move to improve the fuel consumption, I added a K&N 57 Series FIPK Intake and it didn’t make much of a difference except for noticeably more power. Is there any else I can do to improve the mileage? Synthetic oil? Royal Purple for the differentials? Leaving it in the garage? On a side note, my 2001 Jeep Cherokee with the 6 Cylinder(190HP) and On Demand 4 WD didn’t do much better. Maybe it’s a Jeep thing.
Tom & Ray don’t play in these forums. Sorry about that. Just a bunch of enthusiasts, some professionals, and some with a heck of a lot of experience.
While some will talk on and on about the superior performance of synthetics (I like them, personally), they won’t improve your mileage much, if at all.
The only real way to improve the mileage is to park it, or put it on a trailer. Don’t believe any of those commercials telling you to put their unit into your lighter socket, stick this on your intake, or any other bizarre addon. None of them will add anything except some dosh into their pockets, and out of yours.
While some will talk on and on about the superior performance of synthetics (I like them, personally), they won't improve your mileage much, if at all.
I know a guy who changed all the vehicles lubricate fluids to full synthetic. After careful measuring and calculation…he figured his gas mileage improved a whopping .2mpg.
I doubt that that K&N filter is even giving you more power. Have you made and measured multiple 0-60 runs before and after? If you have a MAF sensor in the intake, you could start to see a deterioration in performance as residual oil builds up on the MAF sensors diodes.
“I doubt that that K&N filter is even giving you more power”
But it is undoubtedly giving the OP the perception of more power as a result of a higher noise level!
Only a dynamometer test can determine if you are really deriving more power from that K & N filter, or if you are merely hearing more noise as you coat your MAF sensor with a damaging oil film.