I had black crap in the tank about 10 years ago, clogged up filters etc. Used the biocide (don't remember which one) and after a few filter changes all was ok except for the sender, it would make the gauge jitter all the time. Fast forward ten years, finally pulled that sender and tried to clean it, no luck. Picked up a used one from a gasser, works fine. What surprised me was after all those years there was still some fine black particles in the tank, and the tank and sender were coated with a black deposit that does not wipe off easily.

__________________
Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 120K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
10 Sprinter 3500 chassis with a Class A Winnebago on it. 56K

I have not tried all of those available but at least 10 of them. I read all thee threads and tried Startron. Wow after valve adjustments filters etc ran great ! I went ahead and tried the Startron and after 1/2 a tank noticed huge difference.
Had to change fuel related filters twice but wow. Now when I see it at good price wether I need it or not.
Alan

__________________
92 500E Silver 66k
82 Porsche 911SC 84K
68 Cadillac ( Gone Now )
03 Suburban Z71 200K
85 300SD 217k From Original Owner ( Dad )

x2. I do that once about every 6 months. Pre-filters stay nice and clear.

__________________
http://i284.photobucket.com/albums/l...aman/Fleet.jpg

Peach Parts W124.128 User Group.

80 280SL
85 300SD
87 300TD
92 300D 2.5 Turbo
92 300TE 4Matic