1. What kind of vehicle you have
1997 Grand Cherokee 4.0L I-6
2. What your owner's manual says -- not just viscosity, but certifications (look for acronyms like API SM, ILSAC GF-4, etc.) and change intervals as well
I don't have a owners manual. I know that Jeep calls for a 10w-30 oil
3. Where you live
High desert, SoCal. 2500 ft level. 114f summers to 20f winters at the extremes.
4. How you drive (easy? hard? fast? slow?)
Drive easy, floored to get on freeway, Italian tuneup day before oil changes. Off road easy, trail runs, mild rock crawling a few times a year.
5. What your daily drive is like (short trips? long trips? city? highway?)
Commute twice weekly from 2500 ft level to 4200 ft level then down to 800ft level and then back. Otherwise it's mild city driving the rest of the week.
6. Whether your car has any known problems
No know problems. Doesn't burn a lick of oil during a regular 3000 mile Oil change interval.
If you have any preferences -- synthetic vs. conventional, store-bought vs. ordered online, how long you'd like to go between oil changes, etc. -- or any other info you think might be important, let us know that as well.
No preference, other than what will help to get me past the 300,000 mile mark.
Here's the deal. I bought my 1997 Jeep Grand Cherokee with 197,000 miles on it. I now have 214,000 miles on it.
Previous owner was anal about regular maintenance, oil changes regularly. I have done the same. Oil changes between 3000-5000 mile.
I bought into the "use a heavier oil, Jeep 4.0L engines like it" and used a generic 15w-40 from my past job(major forklift manufacturer branded oil). for first two changes. Then switched to Rotella 15w-40 for the last few changes, due to the "you need zinc in Jeeps" ideas out there.
The last oil change I switched up, went with Pennzoil Yellow Bottle dino oil in a 5W-20 weight. Here's why.
I read a paper about using the lowest viscosity oil that still maintains proper oil pressures. Engines run up to a regular temperature, regardless of outside temp. My engine runs right between 200-210F, regardless of outside temps. The lower initial viscosity will help to get the oil flowing quicker and reduce that "startup wear" that is supposed to be the bigger killer. My engine has always been 20-30PSI at idle up to about 1500 rpm, then 40+ PSI after any RPM above 1500RPM. So I was good for pressure.
As a forklift tech, I understood that the flow is most important, to a point, over pressure. Maintain pressure and flow, your golden. But then further reading, oil shear under loads, Jeep cams grinding themselves up, needing zinc, others say once broken in your golden and on. Now my head is spinning.
One last note, I don't tow or drive heavily loaded. I do understand that if I did so, I'd want the heavier oil to handle the increase loads, temp and others, when doing so.
So, with all that, what do you think? Is it hype about needing zinc for the entire life of a Jeep 4.0L engine? Am I good with a 5w-20? Should I move to a 5w-30, go to factory recommended 10w-30?
Again goal is, 300,000+life on this engine.
Oh, one last note, the "diesel" tick the engine has had while using 15w-40 went away when I switched to 5w-20, I liked that. It has slightly returned now that I'm at the 3000 mile mark on this load of 5w-20. Normal?
Thanks for your time and answers, I'll make sure to stop in to answer any questions posed.
Other than that, I hate this site. It has sucked me in and I have lost DAYS reading through the boards. Still left with my head spinning! LOL.
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