I had a very experienced, independent Mercedes repair shop owner tell me to add one quart of transmission fluid to my fuel tank at fill-up’s. He said the transmission fluid will clean the fuel system and lubricate the injection pump.

I added a quart of Mobil1 ATF and drove the heck out my ’92 300D 2.5T. I drove from San Antonio to the Texas coast, up and down the beach, and back to San Antonio. Round trip is about 400 miles. Highway driving was in the 80mph range and the rest was stop -n- go driving.
I have to admit, there is a significant difference in performance and engine noise for the better. The engine in MUCH quieter at idle.

This particular shop has been in business for over twenty-five years and is considered “tops” in the area.

Has anyone ever heard of this before?

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San Antonio, TX.
1983 300D