I ran a few tanks of B-50 or higher which did clean out my fuel system. I know because after 120 miles of driving I had to change my pre-filter. I should mention that my car sat for several years hardly getting driven at all - so I know it must have been pretty cruddy.

I was still having nailing when cold, and with our cold winters around here the nailing was pretty bad on cold days. I followed the DP in a clear bottle method.

The return was not black, but a dark amber. There was noticeable fine debris floating in the returning DP. My engine got smoother and quieter after only 30-45 seconds, then continued to improve for the next few minutes.

After completing the process I drove the car. First thing I did was drive up the steep hill I live on. There was a noticeable gain in torque. By the time I got to the first turn, I was going almost 23mph! Normally I can't hit 20 on the same run. (18 or 19 more like it) The engine was very smooth and quiet. There was no visible soot coming from my tailpipe. (Before the purge there was a bit of black soot when climbing that hill.)

I've driven about 1200 miles since I did the purge last year and my engine still runs much smoother and quieter. I stored the car over winter last year. I'm still amazed at how smooth and "powerful" my engine is. I hit 85mph on my way home, as my mother followed me in my Camry. Besides being amazingly peppy for a 65 hp car, there was no visible exhaust either.

So I say it's a good product!

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1979 240D, 4spd manual, Power Sunroof, manual windows, 147k miles, Pastel gray/Black MB Tex.
1991 300D 2.5 - Smokes like it's on Crack!