I'll disagree with your post Foredinjection with exceptions. If a motor has alot of build up around the seals where the buildup is acually making the gap smaller. Any oil with good cleaning agents will make it use more oil as the dirt leaves and the gap opens. Note this only applies to seals in poor condition and most likely oil was just added inside of changing

i have an old german guy who does all my serious work to the car and he recomended HD40 or 50. The vehicle is in hawaii so the temp barely gets below 70. I've been running rotella 15w-40 for years, and the engine has about 200k. he said it would idle better and have more power. i've got about 5k on the 40W and it def. performs better. any thoughts of the effects of this oil because i don't really see any posts about it. i imagine the weather has a factor.

O.K, I have taken your advice Forced Induction and changed the oil over to 5W40 Fully Synthentic, but I had an after thought and wanted your opinion: I live in Southern Ontario, Canada and the summer here can be quite warm (25-30c), does this mean my oil will be too thin to lubricate the engine properly on start up (at least until it warms up and gets thicker)? Should I be using 15W40 instead and keep the rest of my 5W40 for the winter? Also, I put Castrol Syntec in my girlfriend's VW Jetta (gas) which is also 5W40 Fully Synthetic, can I use that in my 1988 Diesel Mercedes?:confused:

20W50 Castrol GTX

That is what I use and couldn't agree more with you
No problems and been told by all mechanics it is good oil and is recommended for the 240D

Rotella T
 

Full synthetic 15W-40