I bought my 1982 300 TDT from the original owner (via an agent) in
1993. It had 144,000 miles on it, and I was able to check the
maintenance records at the local dealership where the car had been
faithfully serviced. The engine was running great, and did so for
another 200,000 miles or so. I decided to switch to synthetic oil,
and tried Amsoil. Then later I switched to Mobile One, but not a
product designed for diesel engines.
It may just have been a coincidence, but the engine started to blow
oil out the seals and the amount of blowby increased greatly. I ended
up having the engine remanufactured last summer at Metric Motors in
Canoga Park, CA. I had used Delo 400 from when I bought the car until
I switched to synthetic at about 350,000 miles. I used it for about
15,000 miles (3 oil changes) and the engine went to hell over that
time after remaining stable for 200,000 miles with regular changes of
Delo at about every 2,000 miles. It was using a quart of oil in maybe
2,500 miles, so I usually never had to add oil.
After running synthetic for 15,000 miles, the engine was leaking a
quart of oil every 500 miles. In the case of my engine, it did not
help to change back to Delo, the leakage and blowby continued.
The EGR valve also stuck open at about 390,000 miles, making the
engine impossible to start. I didn't get that diagnosed until after I
had the remanufactured engine in. I don't think that related to the
blowby though or the synthetic oil. I suspect that the EGR valve
stuck because of the reduced lubriicty of the new ultra low sulfur
diesel. I got 396,000 miles on the original engine.
At any rate, I am delighted with the remanufactured engine from
Metric. The head on my engine was cracked in 6 places, so I needed a
rebuild anyway. The car runs like new now.