I posted a picture of the pre-filter I removed from my 300CD a while back after I purchased it (about 1000 miles afterwards).

Recently, I went on vacation to San Antonio. I clogged two pre-filters during that trip (about 2700 miles overall). Clogged one more a few weeks ago and finally decided that it was time to use the biocide and change the tank strainer too. I used Valvtech Bioguard and the next day had a new pre-filter full of the fungus, this time slimy instead of gunky letting me know it had worked it's magic. I waited until I had run the tank near empty and today I drained the tank and changed the tank screen and hopefully my last pre-filter for a while. I took the fuel line loose from the tank and it took all of 2 hours to drain approximately 9 gals of fuel. Once it slowed to a drip, I removed the tank screen and out came another gal. Below is a pic of the tank screen and pre-filter I changed today. Filled the tank afterwards and put some more Bioguard in the fresh fuel. I plan to keep using it (at a maintnence dose) until the bottle is empty.


Edited to fix a couple annoying spelling mistakes

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85 300CD
83 300TD
78 240D (daughter)