I have just had the engine rebuilt. The pistons are the 1st over size.

Tech questions:
1. How will this effect my fuel mileage?

2. Does the car have more horsepower?

3. After driving -Should I wait 15 seconds to turn off the car? For the turbo oil.

4. I have gone about 200 miles and the oil is jet black. I will replace it at 500 miles.

Most important• The break in period

City or highway driving?

The car is faster off the line than my 560sel. I hope that the engine will remain the same. I got to 75 without a problem.

There are many other significant factors that would effect your car's horsepower and fuel consumption besides having 1st size over bore pistons. The over bore size difference is essentially insignificant. More significant things might be turbo boost setting, fuel mixture settings, tire inflation level, lubrication, and so on.

If I were you I would wait for some period of time before cutting off the engine. But this depends on what kind of driving you were doing just before shutting down. If you just came off the interstate to a rest stop, I'd idle much longer than 15 seconds. If you live in a 25 mph residential neighborhood and have to go that speed for five minutes or longer to get home, then that's almost the same as idling as far as the turbo is concerned.

500 miles sounds good for the first oil change after rebuild.

If I were breaking in a newly rebuilt engine, I certainly would not be trying to find out how much power it had over my other cars or running it up to 75 mph.

Here are some break-in tips from one manufacturer:

- Keep your speed at 55 mph or less for the first 500 miles.

- Don't drive at any one speed - fast or slow - for the first 500 miles.

- Don't make full throttle starts.

- Avoid making hard stops for the first 200 miles or so. (This does not apply to you since its a brake issue.)

- Don't tow a trailer during break-in. (Guess that doesn't apply to you either.)

So, in a phrase - "Take it easy"

Your car has had some serious heart surgury. Don't start recuperation with wind sprints or a marathon.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

I plan to have this car for at least 8 years. I will go slow and easy.

Thank you

Nick

NickMendoza,

The oil will turn black very quickly, usually just after starting and idling the car for a few seconds or minutes. Once you get through the break in period give some consideration to using a good synthetic oil (this is not intended to start an oil thread/war). I have been using Mobil Delvac 1 in all my cars and the 1982 240D with 308,000 miles now, has clear oil for up to 45 miles after an oil change. The 1998 E300D TurboDiesel oil stays clear for over 200 miles. In any case, however, it is normal for the oil to turn black sooner or later so I would not fret on that account. Although my first oil change on what was then my Mother's 1972 220D went like yours, so I changed it again immediately after idling the engine for a few minutes. The second fill of oil turned black again right away, which got me really worried, and I called the dealer service dept! They were quite amused but set me straight on what to expect.

Another reason to use a synthetic oil is for your turbocharger cool down concern. I would still make a practice of idling or driving under light load before shutting down just to cool off the turbine housing. Idling or light load lowers the exhaust gas temperatures relative to the temps at heavy loads, and the lower temperatures will prevent cooking the oil that is left in the bearing/seal areas. Synthetics also resist being degraded by high temperatures longer, so a synthetic oil will also mitigate the effects of hot shutdowns.

Good luck, Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Do you change oil at 5,000 miles?

Thank you


Nick