Fuel/water separator filter turning black

[JimT]

So, it seems i'm a little late to the party here.

Before I present an unsolicited product endorsement for my preferred diesel biocide I should point out there are basically 3 reasons you could be clogging up your fuel filters:

Microbial growth, often referred to as "algae", it's actually bacteria or fungi growing in the water of your fuel tank and feeding on the hydrocarbons. This appears to be a bigger concern with biodiesel and blends.

Asphaltenes, a hyrdocarbon often formed when heated fuel is returned to the storage tank. Very common in modern common rail fuel systems. While they supposedly don't hurt the engine, it can clog up filters and, in high concentrations, can actually create thick sludge (like a varnish).

Debris, either from external contamination or often from the breakdown of older rubber fuel lines (more common on 10+ year old equipment, especially if it sat for an extended period of time).

How do you know which one you are dealing with?

Quote:Although both asphaltenes and bioorganisms will look black and shiny, the nose knows. “If you smell the filter when you change it and it smells like diesel fuel, it’s asphaltenes,” he says. “If it smells horrible, it’s microorganisms.” [1]

I haven't spent much time (yet) researching asphaltene treatments and I have no personal experience using them.

As for biocides, my research points to 2 products, BioborJF and Star Brite Bio Diesel. Each is highly effective against different types of microbial life. [3]


Anyway, with the occasional use of a biocide my davco filter no longer turns black. I had a problem not long after getting the truck where the davco would get black almost instantly. Gave her a couple shock treatments of Biobor JF and that cleared things right up. Now every month or 3 I'll add a maintenance dose of Biobor JF and it will keep the filter looking pretty clean for 10-15k miles. It darkens a little, but no where near "black".

There's a bunch of different biocides on the market and based on some articles I read there's really 2 different things that they kill. Most work better with one or the other. I chose Biobor JF due to it's overall effectiveness and it boosts the lubricity of the fuel too. However it should be known that it's technically not approved for on-highway use but farm equipment, aviation, boats, gensets are all ok. Best I can figure from web research it's some EPA pesticide thing. Since I don't follow the EPA guidelines with my truck emissions I figure it won't hurt to disregard this too ;)


Resources:
[1] https://www.truckinginfo.com/156177/keep...fuel-clean

[2] https://www.pbo.co.uk/gear/12-diesel-bug...sted-43353

[3] https://www.practical-sailor.com/boat-ma...-boat-fuel

[4] https://www.practical-sailor.com/wp-cont...CTERIA.pdf

Anyway, if anyone has more "lite" reading, please share!