Jeeps 4.0 OIL

[Zaedock]

My 2.5L YJ cranks over mint with Castrol GTX 5W30, well that is, if I start it with the clutch pushed in. Otherwise, it has to spin the 80W90 in the Granny low tranny and doesn't turn over so easily. Last year, we had two weeks strait of
-20*F and it still cranked over fine.

 

[Ram@Will]

Thanks for all the info,I guess i'll stick with the delo 400 15w40.

 

[99]

Gary, try this to erase the adaptive memory of the PCM.

1. Disconnect the positive battery cable and touch it to ground for 30 seconds.

2. Hook the cable back up.

3. Turn the key to on. Do not start.

4. Turn the headlights on. Turn the headlights off.

5. Turn the key off.

You've now brought the PCM back to the factory default tables and it will run off of them while the the PCM relearns how you drive. Some say it takes 50 starts or warm up cycles and/or 500 miles for this process to be complete. You may have heard this referred to as a forced flash procedure. This is from a Jeep engineer, so it is 100% legit and I've done it on mine without any issues. As far as I know this only works on TJs.

 

[My442]

My sons' 1994 Grand Cherokee gets Exxon SuperFlow 10w-30 and a Puralator filter every 3 months. It has 145,000 miles, and still has 60 PSI of oil pressure.

 

[Gary Allan]

Thanks, 99. I'll give that a try next service. I just had it in the shop too (my buddy's)

I wonder what the static settings will yield in open loop

 

[Ram@Will]

After all this i just remembered my friend use to work at local jeep dealer and he told me ,they would use bulk SAE 30 for oil changes.Also a lot people would complain of ticking or valvetrain noises on the 4.0 and i think also on the Magnum engines(3.9/5.2/5.9) and this stuff i guess quiteted the noise down. Any Comments on SAE 30?