My 1991 300D 2.5 has always had a very loud pinging problem, that nobody has been able to solve. I had tried everyones advice such using Diesel Purge, pulling the intake and having it cleaned by a machine shop, new injectors, new delivery valves, verifying timing was correct, checking valve specs, fuel pressure, etc..

I read on this forum that you can use Chevron Techron in diesels, so I put a bottle in because I had great success with it in my gasoline cars. My father-in-law had to use my car for a few days while I did some work on his. When he returned the car to me, I knew something was different, but I could not figure out what, until I pulled in my garage and I could here my Wife talking inside the house. My diesel sounds my neighbors E300D (98 I think). It is absolutely quiet.

I don't want to discount anything here, but this is what I think happend.
I put the Techron in the car, my father-in-law drove the car on ver long trips each day (250 miles+) and he drives cars very hard, or as he puts it, "the way a diesel is meant to be driven." He used to have a diesel and he always tell me that I need to "run" the car and my "old lady" driving habits are hurting the car. The car never had a running problem, but the noise was very loud, now it is much, much quiet, almost like a gasoline car.
Could have the Techron + long drives do all this???

If there was that much carbon built up on the tops of the pistons from lugging the engine and using questionable fuel, YES. A fuel additive can help.

We install a fuel additive at EVERY major service.

__________________
Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS

I am truly amazed, it sounds like an entirely different car. By the way, what fuel additive to you use?