I now have almost 3,000 miles on my rebuilt 4.0. It runs like a beast and I love it, it's just using oil. The valve cover is leaking a little but not much. I'm having to add a quart every 800 to 1000 miles. There is no smoke that I see. The exhaust is normal. No other oil leaks other than the valve cover. I am running partial synthetic 10w40. I don't know if it matters but the motor is bored .30 over and has an erson cam. It was built by a very reputable shop amd like I said early runs like a beast.

I don't figure this kind of oil consumption is normal. The motor was properly broken in. Could it take 2500 to 3000 miles for the rings to seat?

 

I would take back to the shop because that's alot of oil being used . you would run out of oil between oil changes if you did not add oil to it . I have build alot of engines in my life and only had one do that and had to fix it and found out that the valve seals were missing and after installing the seals it only used 1/2 a quart between oil changes and the engine only had about 1500 miles on it and used less as it got more miles on it .

 

Synthetics are sometimes not recommended for engine break in oil so I have heard. you want a break in oil. cylinders may have lost cross hatch pattern, which can lead to high oil use.
Burnt oil will eventually ruin your catalyst$$$$$$$.

a boroscope may give you a view of the cylinder walls.

leak down test will be helpful to see if blow by is issue with rings.

good luck

 

Probably a stupid question here, but I have only run partial synthetic oil in it. Even for break in. Should I change it to conventional oil and run it for a while and see if maybe that will help? I have a 500 mile road trip coming up next weekend and maybe that long of heat cycling and regular conventional oil might help? I'm grasping at straws here. I hate the thought of tearing into my new motor

 

compression test

 

imo, its critical you consult the rebuild shop about this matter asap