dbgrate,

Biocide treatment only needed if fungus is in the system. If the car has never been filled with fuel contaminated by fungus, there wil be none in the fuel system.

In about 10 MB Diesels over the last 35 years, I only had a fuel fungus problem in one car. You don't have to replace the fuel filters unless you notice a drop in engine power, usually on a long hill where the engine is burning the maximum amount of fuel.

Another test is to remove the rubber fuel line from the tank where it connects to the steel fuel line. If the fuel comes out in a steady stream, the fuel strainer in the tank is not plugged with fungus and you don't have a fungus problem. If the fuel comes out slowly, the strainer should be removed and cleaned. If there is a brown silicone like substance on the strainer, a biocide treatment is needed.

P E H