300D Rebuilt Diesel Engine

City driving is the best... highway is the worst type to break in engine.

Lots of speed and gear changes, presumably? And not too high a speed, say above 60 mph/100 km/h.

That's certainly the advice I got from Merc when getting new cars some years ago.

Run-in distance approx 1000 miles.

Would you agree?

DAS

To send an e-mail directly replace "spam" with "schmetterling"

Yep... speed, gear and RPM changes. High speed is not the issue... the issue on highway is constant RPM.

500 miles is enough.

Thanks, and that works great for me, as I do very little highway driving anyway. Mostly in town, streets, hills, etc.

And about oil--I would like to switch to synthetic this time around. How long should I wait to switch to syn after the break-in?

Exactly how does a somewhat constant rpm for a period of time cause engine problems, knowing that changing rpm and gears are required to get you on and off the highway?

Piston rings cannot seal properly with the cylinder wall if constant RPM speed exist. Constant speed will smooth out the cylinder wall to the point where it cannot bed properly.

Look, it is only 500 miles of your engine life that affect the remainder of its life. If that is too much to ask, then I don't know what to tell you.

I would wait till second ol change just to be on safe side... which is a couple of thousands of miles.

All new MB are equipped with synthetic fluid from new. MB said they engine will bed itself properly regardless of how good synthetic oil is. Maybe they texterized their cylinder wall differently that will promote proper bedding. I don't know. I do know that it does work... as our 2001 E320 was synthetic from day one.

Tiger, I know you like the 500 miles but on more than one new Merc the advice was 1000 miles (well, 900 miles/1500 km to be precise). Then change the oil to the normal one, having first used a thinner one, IIRC.

AND they said keep the speed below 60 mph/100 km/h as mentioned before.

I agree with you about the engine life. It's got be worthwhile.

I even have a personal anecdote (which I mentioned in this forum a loooong time ago). In 1980 I received a W123 200D as a company car (in Germany). Everybody at my level and one above got one of these, so there were quite a few around. At meetings the car park used to look like a 200D showroom. Anyway, a number of my colleagues were impressed by my top speed, an indicated 143 km/h. Nobody else could reach that, apparently, and the officially listed top speed was a bit below that, though I can't remember what.

I put it down to very careful running in!

This is what we are talking about here.

(Yes, it could also have been a badly calibrated speedometer, I know I know...)

In recent times I have chatted to Merc mechanics about the passing of recommended running-in periods. They said it's still advisable to drive them as if running them in. Maybe in this case 500 miles would be enough.

To the OP I would say, you have seen the two opinions, choose. At the very least take Tiger's advice and run in for 500 miles. Whilst that may be less than optimum from what I know, it is a lot better than nothing at all. You owe it to your engine.

DAS

To send an e-mail directly replace "spam" with "schmetterling"

Ok, this sounds good. I wanted the rings well seated before the switch. I will break in to 500 miles, change, using petroleum oil again, then go to syn at 2,000. I want to make sure this engine goes the distance, which the original did not, I believe due to faulty valve adjustment.

Thanks again for this very helpful advice.

Ok, this sounds good. I wanted the rings well seated before the switch. I will break in to 500 miles, change, using petroleum oil again, then go to syn at 2,000. I want to make sure this engine goes the distance, which the original did not, I believe due to faulty valve adjustment.

Thanks again for this very helpful advice.

Synthetic oils are better at filling in microscopic pores in the cylinder walls than petroleum oils. That's what causes the rings to have proper bedding. If you switch to petroleum based lubrication, you may have slightly increased oil consumption because the microscopic pores in the cylinder walls will become exposed.

AMSOIL recommends if the engine came new with petroleum oil to keep it until the first oil change so that any metal particles from manufacturing will be captured in the oil filter or drained when the first oil change is completed.

If the engine was filled with synthetic, there is no reason to change back to petroleum for a break in period. Just change the oil and filter at a shorter interval than would be normal. After a rebuild, changing the oil and filter at 3,000 to 5,000 after the rebuild should be sufficient. After the first oil and filter change, proceed to the recommended oil and filter change intervals using regular synthetics OR use extended drain intervals if using AMSOIL synthetic oil and synthetic nanofiber oil filters designed to trap particles down to 1 micron in size. Regular oil filters are designed to trap particles down to 5 microns in size. Using AMSOIL synthetic nanofiber oil filters will allow the oil to stay analytically clean. With AMSOIL synthetic nanofiber oil filters and oil analysis, just change the filter and top off the oil.

If you want the absolute best protection available, AMSOIL synthetic lubrications are the way to go. The additive package in AMSOIL cause lower friction which in turn cause less heat to be generated when metal parts slide against each other - and less wear. This causes increased fuel economy and better emission control since the engine is running at the optimum temperature.

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I do use AMSOIL, although I have never been able to determine what the AMSOIL equivalent part number is for the oil filter on the Mercedes- Benz 300D 617 engine. If you could provide that information, I would greatly appreciate it.