What type oil are members using in your 1997 and newer Jeep 4.0 liter engines?
I'm curious to know. I have heard some people say great things about Shell Rotella (5)?? Diesel oil... I've read that some don't like it.
Since these 4.0 engines are hydraulic flat tappet pushrod style, don't they require a
certain amount of zinc in the oil, to protect the valve train, and camshaft?
Wouldn't oil such as Joe Gibbs "Hot Rod" muscle car oil, like their 10W30...work well in Jeep 4.0's?
What about the cat converter, would that fair well with that type of oil?
TIA

Hi , My 2004 Wrangler Sport 4.0 with a 5 Speed has had VR1 10W-30 and a Napa-Wix 1515 Big Filter for the last 100,000 miles I have owned it . Currently has 222,000 and is quiet as a church mouse !

Ronnie...is that a synthetic oil? Or conventional?

I've had a few of these.
All went well over 200k on a diet of year round 10w40 conventional.
Used to be Valvoline until it went out of my range price wise.
Then it went to farm and fleet store brand. Changed every 4k miles, I am very insistent on that... And every oil change done by ME. Nobody else.

Volaredon.... using conventional 10w40 in yours.... the engine doesn't make any
"tractor" type noise, from what I have heard people mention? I would just like to protect this new Jeep I bought..
for many years to come.

Hi RR , The silver bottle with 10W-30 Part Number 822388 is Conventional Oil with Lots of Zinc & Anti wear Additives in it . Buy it at NAPA when it's on Sale for $5.99 . Great Oil for a Good Price .

The 4.0 traces it's lineage back to the early 60s. They were fine without synthetic then.

Personally I think people are making too much worry about zinc levels. For break in it's necessary and if one is running stiff springs or a race cam you're better off with it. But, typical daily driver OEM engines are fine without extra zinc. Soft springs and well established wear patterns minimize the need.

I'd also recommend 5 30 so it pumps to the top faster than thicker oils.

Most of the tractor noises I've heard from these are exhaust manifold related.

Thanks guys for your input and recommendations. I really am not concerned about
synthetic vs. conventional oil... more thinking about using an oil with zinc included, since as you
all know, these 4.0's are old school pushrod, hydraulic flat tappet cam engines.
I think I may start using the VR1 oil... and try it out.