I am almost done swapping a rebuilt 940 turbo motor into my '92 wagon. The engine shop doesn't offer any advice on what kind of oil to use for the first 500 miles. My plan is to run this car on Mobil One but I've heard that isn't a good idea for the break in period as synthetic oil doesn't allow the rings don't seal properly.

I remember back when you bought a new car they put a break in decal on the windshield. Am I the only one who remembers those?


Any experience or sage advice for me on this?

This may seem obsessive to some , but on a freash rebuilt, I always fill with regular oil of recomended wt, run without load ( idle in the driveway) for 10 or 15 minuits, and drain it and change the filter( this is to get the leftover chips etc out without grinding them into the bearings).
Then drive lightly for 100 mi and dump again.
Then run 500 ( still refraining from flooring it )and change again.
then run 3000 mi and dump it and switch to the synthetic.
For break in , just about any of the quality petrolium lubes will do.
Avoid the temptation to use cheap filters for the break in period, this is when you need good ones most.


------------Robert

Synthetic is ok from the beginning. if you have any doubts then conventional oil for the first few hundred miles certainly won't hurt anything. You really can't go wrong either way.

I'm curious to know why you had to replace your engine.

Good luck!

--
Matt L. -- Cary, NC -- '89 740 sedan -- '91 740 wagon

Do not use synthetic oil for breaking in the engine. The extra slickness of the synthetic will keep the rings from breaking in.
--
john

Oops I was wrong, thanks for the correction. The Mobil-1 website says to break-in a new engine with conventional oil, then switch to synthetic.

I was thinking that synthetic was OK for break-in, because some new cars now ship with mobil-1 from the factory (like corvettes). I think rings will eventually break in OK with synthetic, it will probably just take longer.

--
Matt L. -- Cary, NC -- '89 740 sedan -- '91 740 wagon

I would expect that any engine shipped with synthetic oil has already been test run under substantial load in a test cell, and the rings are already broken in. Some cylinder coatings (trade mark Cerminil in aircraft, a ceramic/nickel coating) seem to be immune to break in troubles and piston rings are even re-installed and re-used when the piston has been removed from the bore.
--
john

tks matt,

the original engine overheated enough to warp the head. The engine had 177K on it and I thought why spend $1K on a head job when I could have an entire rebuilt for $1500 more.