What is the best oil for my 1997 Jeep Wrangler TJ 4.0?

I returned the Rotella T6 I had in the garage and bought Valvoline Full Synthetic High Mileage with Maxlife technology based on this:

https://540ratblog.wordpress.com/2013/06/20/motor-oil-wear-test-ranking/
I've since joined the camp that believe zinc concentration is meaningless, and instead concern myself with film strength, which is a measurement of the oils ability to stay put instead of being squeezed out between the cam lobe and lifter face surfaces. Gasoline engine oils seem to fall mostly from the 80-120kpsi range, while most Rotella (and diesel oils in general) are bottom of the barrel in this metric at 70k and below.

It probably matters on high-revving race engines, but will it amount to a hill of beans for a 20 year old 4.0? Probably not, but the valvoline I bought was the same price so a little extra peace of mind isn't costing me a dime.

Its hard to find what your looking for on that page. But I skimmed through it. Some interesting information in there. Maybe zinc isn't the end all be all we thought it was.

I may switch to the Valvoline Full Syn High mileage as well. I always liked Valvoline in the past with other vehicles. I'll have to give it a try.
 
Its hard to find what your looking for on that page. But I skimmed through it.

That's no lie. The guy is clearly not a web dev or a graphic designer. I probably spent a good couple hours on it and still skipped some chunks.
 
OK so on the topic of zinc in the oil. Where did that idea come from that modern oils do not have enough zinc. How much zinc does that source say is needed? I just came across this youtube video the other day where I guy opened a fresh can of oil from sometime in the 1950s. He ran several test comparing the old oil to its modern equivalent and also sent in a sample to a lab for testing. That oil only had zinc levels of about 581. That is actually lower than a lot of oils on the shelf today. So that makes me wonder what the typical zinc content was in oils in the 80s when our 4.0 was developed. I'm starting to think that I have been chasing the wind worrying about zinc levels in my oil.

 
I returned the Rotella T6 I had in the garage and bought Valvoline Full Synthetic High Mileage with Maxlife technology based on this:

https://540ratblog.wordpress.com/2013/06/20/motor-oil-wear-test-ranking/
I've since joined the camp that believe zinc concentration is meaningless, and instead concern myself with film strength, which is a measurement of the oils ability to stay put instead of being squeezed out between the cam lobe and lifter face surfaces. Gasoline engine oils seem to fall mostly from the 80-120kpsi range, while most Rotella (and diesel oils in general) are bottom of the barrel in this metric at 70k and below.

It probably matters on high-revving race engines, but will it amount to a hill of beans for a 20 year old 4.0? Probably not, but the valvoline I bought was the same price so a little extra peace of mind isn't costing me a dime.
He also recommends 5w30 across the board. Is that the weight you're running? Based on the user manual, I'd choose 10w30, but I'm open to thoughts.
 
Increases oil capacity slightly, can pass oil a bit easier, there's room for it, so why not?
It adds an ounce or two, nothing to get excited over. And a larger filter would only be able to pass oil easier if the oil hadn't been changed in so long that the filter was close to being totally clogged and about to go into bypass mode.

More filter surface area only allows it to filter longer, not better. A bigger screen door isn't going to keep the dust out of the house any better until it starts getting clogged with dirt. 😊
 
He also recommends 5w30 across the board. Is that the weight you're running? Based on the user manual, I'd choose 10w30, but I'm open to thoughts.

I'm running 5w30. I do agree with him that 5w will get oil circulating more quickly which is always good. Once they're warmed up, there should be no difference between the 5w and 10w.

I was not pleased with the valvoline, as it made my lifter noise noticeably worse. I'm back to Castrol gtx high mileage.
 
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While we're on this subject, is there a larger oil filter than what's specified? Plenty of room, might as well use a larger filter.
I know it's been a bit since you asked, but I use the Motorcraft fl-1A. It's a bit longer, and was the filter design used by millions of domestic vehicles spanning several decades, so it's in stock anywhere that sells oil filters.
 
I know it's been a bit since you asked, but I use the Motorcraft fl-1A. It's a bit longer, and was the filter design used by millions of domestic vehicles spanning several decades, so it's in stock anywhere that sells oil filters.
I found the Wix 51515 - works fine.
 
My TJ only has 36,000 original miles, but I use a high mileage formula 10w30 Dino oil just in case it might help all of the gaskets & seals to last longer. ‘Couldn’t hurt & a lot if folks here do the same. My Jeep doesn’t drip, smoke or use any oil. 👍
 
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1997 wrangler 4.0/ I tried Rotella, Mobile one, and wal-mart's. All worked fine but still had these small drips. First time I swapped to Vavoline high mileage 10-30, just about shut down any drip I had. I am not picky about alot of things, but I believe whatever oil and filter you use, just make sure it stays clean and your engine will be much happier. If you don't have drips or leaks, the wal-mart oil and their filters stay exceptionally clean.
 
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