New Crate Engine Oil After Break-In

JEEP GC

Member
Joined
Jun 19, 2021
Messages
54
Location
Charlotte
Recently installed a new S&J 4.0L engine in my 1997 TJ 4x4 5-Spd. Used their recommended break-in oil for the 1st. 500 miles. What oil should I use after the initial break-in period...Thanks
 
Conventional 10w-30 seems to be the consensus. I prefer Valvoline VR1 for the higher ZDDP content. Many oils without that and have thousands of worry free miles.
 
  • Like
Reactions: JeepingNet
The good news it that the low lift cams in the 4.0 don't have the problems with the new oils that the old high performance flat tappet engines do. So you are probably OK running any 10w-30 or -40 after break in.

VR1 is probably the best conventional with high ZDDP that should be fairly easy to get.

All the newer energy conserving, emissions friendly oils have much lower levels of Zn and Ph (ZDDP) in them and aren't great for flat tappets or distributor gears.

Oils 40 weight and above are allowed a higher amount.
 
  • Like
Reactions: SkylinesSuck
I almost completely agree with that.
The good news it that the low lift cams in the 4.0 don't have the problems with the new oils that the old high performance flat tappet engines do.
I'd say they don't have as many problems, but I ate a lobe off my stock cam way back when. Somebody just posted about it happening to them just the other day. I've seen it happen every once in a while, but many 4.0s go for hundreds of thousands of miles with no issues.