The older I get, and the more I learn about fuel issues, the less I think I want to know. It turns out that home heating oil has a fairly large issue with "sludge" formation. Apparently the heavier petroleum components want to conglomerate and will eventually solidify. There are additives to dissolve sludge, and additives to prevent sludge, and additives to kill bacteria which feed on sludge. Since this sludge forms from heavier molecules in the oil, it's not like a sediment that gets filtered out. Instead it deposits on components when the fuel is at rest and motion free. It can build up so badly that gear type oil pumps cannot be turned.

Now I've worked on diesels for years and I've cleaned up a few dirty systems, but what we get is nothing like what can build up in the tank of a home system. I've been dealing with an issue that appeared to start after I added 40 gallons of B100 to a 275 gallon tank in '07. Finally, yesterday, I decided I needed to get this resolved once and for all. I almost wish I hadn't.

I have a 1 quart, 2 micron filter in line. The water heater flows .75 gallons per hour when it's running, approximately 11 minutes each run, maybe 10-12 times per day on the high end? So we're filtering 3300 gallons of fuel per year. The tank was new in '05 although the lines have been in service since '84 or so. The filter was installed approximately a year ago.

After fully servicing the burner I found no fuel to the pump. After a series of tests, I removed the filter to check for restrictions. It was packed full of "sludge." And yes, it looks very much like what you'll see inside an old diesel line or tank, but much, much thicker. The vacuum gauge on the filter had not indicated restriction, probably because the port to the gauge was packed with sludge. I know from experience that solvents such as acetone, laquer thinner, carburetor cleaner, MEK, and xylene are all effective at dissolving this deposit with varying degrees of success so I set about cleaning the filter in order to get hot water back for a day or so until I can pick up a new one. After visibly inspecting the lines at the tank and the filter, I am determined to "flush and clean" this system in the hopes I can end the two month cleanings now required to keep the water heater running.

The reason I'm posting this here is mainly for education. It's sometimes hard to get information about the differences between diesel fuel and heating oil. They're often thought of, and sometimes described as, very similar in many regards. This tendency to build "sludge" is a significant difference imo. I know that dispersants are added to vehicle fuel similar to what's added to diesel oil. These dispersants may play a part in keeping diesel from forming sludge. Or the refining process may be different enough between the fuels so diesel doesn't have the same tendency to form sludge. Home heating oil additive companies are as secretive about their ingredients as the vehicle fuel and oil additive companies. General talk of keeping molecules apart combined with references to surfactants and solvents are about all we get for clues. MSDS sheets give a minimum of safety information and hide much under proprietary formula entries. Patent searches may turn up more concrete information but I don't know that I'll spend time to dig further. Ultimately, I'm looking for a solution (one that will stay in solution) and I'm beginning to believe that buying a tank of diesel and applying for a rebate for the road taxes might just be the way to go. The diesel fuel price fluctuates more often than fuel oil so if I play my cards right I might even save money.

I wish I'd taken pictures. There were a few "Whaa??!" and "Wow!" moments during the inspection and subsequent cleaning.

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When life gives you lemmings... make lemmingade.