Primary fuel filter

[JimT]

Since DEF was mentioned I'd like to remind people that the DEF filter also needs to be changed out regularly.

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Which biocide do you use? There are different things to treat for and some biocides work better on some than others.

Here's a great article on the subject. Not a highly detailed test setup, but the conclusion helps clear up what the results were.
https://www.practical-sailor.com/boat-ma...-boat-fuel

This article is a bit more scientific and the products are mostly availble in the UK, but still an interesting read (well, I found it interesting, not everyone will share my opinion).
https://www.pbo.co.uk/gear/12-diesel-bug...sted-43353

I personally use BioborJF. It cleaned up my tanks when I first got the truck and I do a maintenance treatment every once in a while. Especially since its hard to avoid all the bio-diesel blends out here which help accelerate the growth. Supposedly BioborJF is not actually approved for use in on-highway vehicles. After some research I found that it has something to do with the EPA and pesticide and not about any kind of engine issue. So, I use it anyway. It works well but the dead biomass will clog up the filters quick so expect 2-3 short filter replacements before things return to normal.

I actually need to do a shock treatment. After my last filter change I filled up with the mandatory bio-diesel blend sold in CT and then truck sat for almost a month with that same fuel in the tank. Now after 4,000 miles the davco 10-micron filter turned black and the fuel is half way up the filter already. The previous filter had 25,000 miles on it before it needed to be replaced. Amazing how quickly it can change.