Ok I bought some Rotella 5-40 synthetic oil for my 2001 Cherokee with the old school 4.0 engine. I was wondering if this is a good oil? I know Rotella has a bunch of detergents in it and some zinc in it still. So is this a good oil or did I buy some crappy stuff?

Good oil.

Kevin

Used it in my diesel and all non-roller gas motors. Doesn't have as much zinc as it used to, so an additive may be a good idea for a flat tappet cam, especially during break-in.

I use Delo 400. I just checked again last week, and the 15w40LE DOES have enough zinc/phosphorus to work fine with flat tappet cams.

Rotella is excellent oil.

I dump whatever cheapo oil I can find into my jeep's 4.2. These old school cams are not that aggressive for oil to be a huge issue on them.

I started out with 15/40 rotella with my flat tappet mechanical cammed 416. All went well.

Went to 10/30 and actually quieted down the lifter noice some. I was looking to lower oil pressure and free some HP. Noise reduction was just a bonus. I add JB Engine Treatment for zinc replacement.