Fresh engine- what oil?

[Bonnewagon]

This is about a Jeep engine but would pertain to all engines. I got my 4.0 back from the shop and it is all rebuilt. The machinist said to use a dedicated break-in oil with ZDDP first and change it as soon as I was satisfied everything was working properly. Then to use the same type break-in oil for the first 500 miles and then change it again. Then to use a good dino oil for the next 2000 miles. After that I could switch to full synthetic oil. I am scared of ruining this fresh engine by using the wrong oil. I don't want to start a pissing contest over ZDDP content either. This XJ has three Cats and I know ZDDP is bad for them. I noticed these 4.0 engines use single valve springs. That would indicate light spring pressure on the valve train. So maybe ZDDP is not all that important. The factory manual recommends an API certified multi viscosity oil but does not indicate which one. It also says to use an ENERGY CONSERVING oil such as 5W-30 or 10W-30 depending on climate. So can I get some real-world experiences from guys who have broken in fresh engines? What oils did you use for good or bad? I did do an exhaustive search and opinions are all over the place. I found this info to be the most intriguing. https://540ratblog.wordpress.com/

 

[fleming442]

If it's too slippery, the rings won't seat correctly and you get blowby, so no synthetics for a while. I wouldn't worry about the break-in if you're reusing the valvetrain and cam.

 

[xylorex]

If it's too slippery, the rings won't seat correctly and you get blowby, so no synthetics for a while. I wouldn't worry about the break-in if you're reusing the valvetrain and cam.

What's your opinion if all you're changing are the heads / cam / lifters? (Asking for a friend haha)

 

[fleming442]

Roller or flat tappet? Aren't the 4.0 AMCs OHC? Did they have non-roller followers?

To answer your question: I don't plan on ever using another flat tappet cam for a couple of reasons. The metals are softer from overseas and the oils aren't made for it anymore. Too many hoops to jump through just to have a flat lobe lingering in the back of my brain.

 

[Doug Chahoy]

My mechanic had me add 1 quart of brake in oil to 4 quarts of Castrol GTX 10W30 till we got it timed. Then changed filter and oil to just the Castrol

 

[lilbowtie]

Not going to tell you how to break-in your engine or what oil to use, but will say I use Brad Penn w/ high zinc and have never had problem or wiped a cam in my whole life (and I'm old). Sounds like you have done some investigating and sure you have read you can have too little and too much zddp. I'm sure you will make a good decision and if your running a new cam and flat tappet lifters, use a proper flat tappet cam break-in procedure.

 

[pontiacgp]

with the break in procedure the machined suggested he is not worried about the cam and lifters so he must have reused the lifters in the postition they were in when he dissasembled, The only reason for the ZZP is the valve train break in so I don't think you need to have alot of it during the time you are first running the engine. I would double check with the machinist to make sure I wasn't missing something

 

[melloelky]

I would go back to the machine shop and ask specifics.what brand,what weight.ask them to elaborate on what they recommend..they set clearances and everything else inside this new engine.follow it to a T that way god forbid something goes wrong.you jumped through all the correct hoops and did everything they told you to do.that way you're safe.

 

[Bonnewagon]

The head is new. Springs are new, rockers, pivots, pushrods are new so fresh valvetrain. The block is rebuilt with new pistons, flat tappet cam, bearings, new lifters yet to be installed. So in 2001 there was still a good amount of ZDDP in the oils. What I read is that it isn't as if there is NO ZDDP- it's just so little that it won't kill the Cats. And that they are using different anti-wear additives that won't kill the Cats. I like what 540rat says about using an oil that has INCREDIBLE (his term) anti-wear characteristics, anything over 100,000 psi. He says a lot of high zinc oils do not have good anti-wear ratings. I think I will use an oil from his charts that has superior anti-wear yet still has a good amount of zinc, but not so much as to threaten the Cats. I don't even want to think about paying for three new Cats that will pass Cali/NY emissions. EDIT: the builder believes in ZDDP additives but then he is mostly involved in racing engines with crazy cam loads and no cats. EDIT: He did recommend Red Line, Brad Penn, and Comp Cams break-in oil. Basically anything with a lot of zinc.

 

[pontiacgp]

I always ran an engine for 20 minutes on it's first start alternating the speed to break in the lifters and cam and then dump the break in oil.