Just wanted to ask if there is a specific time when u need to overhaul a motor or does it depend on the condition of it?
We have a 1989 300TE with the M103 motor. The car is super smooth throughout the rev range, but today, i was driving behind my dad who was driving the car and he wasnt really pushing it and all this black smoke was coming out...It has 290,000 kms and it drives beautifully..Its just that the black smoke dont look too good thats all... I was wondering if anyone has suggestions?

Thanks
Chris

1989 300TE
1997 C200 Elegance
2000 ML430