Well.. The long awaited period has arrived.. The new rebuilt motor has arrived for my 91 350sdl. It will be installed in the next few days and hopefully my boat will be back on the road next week. The big question that has crossed my mind is the break in period for this engine. Anyone have any good suggestions or guidelines for breaking in a newly rebuilt Diesel Engine? I want to do everything possible to make this baby last for a LONG Time.

When I had an engine rebuilt (new pistons, bored one size over std, rebuilt IP, new cam etc.) I was eager to use synthetic oil in it. The advise from my mechanic as well as RedLine, the oil co., was to NOT use synthetic oil, rather use 15W40 Dino oil for the first 3000 miles, then go synthetic. You want the rings to wear in so the added slippery nature of synthetic is not desireable I suppose.
And it was suggested I baby it, not to rev the engine over 3000 RPM. All seems good advise and I followed that too.
Oh yes, I let the engine warm up for half a minute - that's all (it wasn't at all cold here either.)
Good luck with the new engine!
DDH
1971 220 (gas) 4-spd manual 104041
1979 300TD w/ ’85 turbo engine 294050
1983 300D 240700
1985 300TD 215225
1987 300D 258K

__________________
'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

Take a long, at least 250 mi., trip at good highway speeds. Drive it as easy as a Sunday afternoon driver. Then change the oil right away. Then repeat this again. Short trips, where the engine barely gets to operating temp., should be avoided for the first 1000 miles. I think you will be pleased with the results!

__________________
Sam

84 300SD 350K+ miles ( Blue Belle )

vary engine speed ?

Yeah vary the engine speed it allows the bearings to break in better. I would change the oil at 500 miles 1,500 miles than at 3000 maybe you can go synthetic. Many people have told me that synthetic should not be used during break in.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I've heard this a couple of places: when the engine is warm and brand new use full throttle full load full RPM for a couple of acceleration cycles to seat the rings.

TurboDawgs,

Doesn't MB install Mobil 1 synthetic oil in most of the new cars they build? If they do, this should answer your question.

P E H

It is amazing all the recommendations there are for new engines. Run them easy, run them hard, etc., etc... The synthetic oil question comes up on the Duramax forums I read all the time and the general answer is to wait until at least 5000 miles to switch. A couple guys who put synthetic in right away have reported seeing a little more oil use over time then those who started with dino (doesn't necessarily mean that is going to happen each time, but it has been reported anyway). To me, it makes sense to start with dino anyway, since I would change the oil after the first couple hundred miles just to be sure to get rid of any leftovers from all the machining and assembly. If you are going to change it a couple times, it makes more sense to use cheaper dino, then switch to expensive synthetic when you are going to leave the oil in a long time.

__________________
Keep everything as simple as possible-but no simpler--Albert Einstein

I don't agree with this but AMG does say run them hard out of the box, and they start them on Mobil 1 from birth. But they also don't recommed the first oil change for 15k miles. Now this is just me but I would not want to push a 500hp twin turbo V8 hard for the first 1k miles.

Not using synthetic during break in maybe it is an old wives tail but what is the dig deal with running dino? It does not hurt anything. What would you gain by having synthetic in their for the 1st 3k miles?

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Ditto with what Jim Anderson posted. Give the car brief half to full-throttle accelerations in the higher gears. Piston rings are designed to push outward against the cylinder walls from the combustion pressure. This increased pressure from high-throttle conditions will help burnish the piston rings for a good seat. Some have even reported that the cross-hatching on the cylinder walls acts as a file against the rings. I personally think that thought is 'a little over the top'.

You want to vary your speed so you don't develop a sharp ridge on the cylinder walls where ring travel ends. The piston/conn rod assembly stretches differently at different rpm's.

In short - don't baby it, yet don't go all out in low gear.

__________________
95 E320 Cabriolet, 159K

...and nothing but constant-speed highway travel won't let it build a proper wear pattern. Mild city driving and different conditions are the best way to start off well.

Do Not use Synthetic oil till you have at least 5000 miles on engine using dino.
Drive car as you do normally. Is this engine a MB rebuild or did you have it done by someone else?