So the fuel tank in my SDL has always been spotless, even after sitting for 10 years with 1/4 tank of fuel, the inside of the tank sparkled. I use pump #2 only and I don't use any additives, occasionally I'll throw in a shot of 2-stroke oil, but that's about it.

Towards the end of December I wound up with a truly terrible tank of fuel. I filled up on the way home, and by the time I got to the house, the engine was already clattering like a sick tractor. The following morning, the cold start was really rough and the knocking was bad enough I thought the car had a rod knocking! Some "Power Service" additive helped a little bit, but it was still pretty rough as I used that tank up (takes me 3-4 weeks to use a tank with my driving habits).

Flash forward to now (about 6 weeks later) and I notice a few little black "chunks" in my prefilter. It's always been spotless since I put the car on the road in 2016, so I'm drawn to assume that rotten tank of fuel is my culprit.

I want to treat the tank, even if it isn't bug/algae/fungus/whatever just to be safe. I went to Vato-Zone and asked for a treatment and they looked at me like I was nuts. All they seem to have is injector cleaners and cetane boosts! I found treatments for ethanol and plenty of stuff for gas engines, but not a single biocide for diesels.

What's good, where do I get it, how often do I need to treat? I've never dealt with this before and I want it gone.

And yes, I went and complained to the fuel station I got the crap fuel from. Their response: "How do you know it was our fuel?" Won't be using them again.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]