Winter Diesel Gelling and Biodiesel

Reader Contribution by Bruce Mcelmurray
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Adobe Stock/José 16
What potential biodiesel disadvantages exist? Learn what biodiesel can do to a fuel system if not properly treated against gelling.
One would think that living in a gated community plus living remotely that we would not have a problem with vandalism. Unfortunately, that is not the case. In three years, we have had two episodes of vandalism, and the last one was diabolical and costly.

The first one happened to our log splitter, and in that case, someone put a substance in the fuel, opened the gas shut-off, and gravity feed did the rest. I was able to repair that myself so the cost was moderate. This time, the vandal sabotaged our new Kubota tractor. It took considerable effort to first determine it had actually been vandalized and second to determine how it was done.

A few nights prior to the vandalism being discovered, the dogs alerted us to something outside, so I took the flashlight and went out to investigate. I was looking for a coyote, bobcat, wolf or perhaps a mountain lion. I did not think to look where the tractor was parked as we were not anticipating any human being present, plus the area is partially enclosed.

A few days later, I was clearing some new snow with our 6-month-old tractor, and it began to sputter and lose power. I parked it and called the dealer. I was advised that perhaps the diesel fuel needed to be treated with an anti-gel compound, which we promptly did again. I had already treated it once, but the theory was the anti-gel may have been beyond its shelf date and had lost it potency.

It started and ran for a few minutes the next time I used it, but then it stalled in the middle of the driveway. The dealer sent out the mechanic, who warmed the tractor up with a large heater and also treated it again with anti-gel and got it running, albeit rough and lacking power.

A few days later, I went to use the tractor and once again; it stalled and would not run. The mechanic came out again and this time both filters were replaced and all the fuel drained from the tank and the system was purged of all diesel fuel. With fresh fuel and new filters installed, the tractor ran normally again. The photo shows the two filters which are a plastic housing with a paper filter inside. In order to see what had actually clogged the filters, I cut them open. This began my education on diesel fuel.

Petroleum-based diesel has a cloud point, and when you purchase it, the dealer should have already pre-treated it for winter. If temperatures drop below 10 degrees Fahrenheit, it should be additionally treated by the end-user with anti-gel, which can be bought at any gas station. That treats the diesel fuel so it will not gel and fuel will move normally through the system.

Biodiesel Gelling

Biodiesel, which is a practical substitute in most instances, is just like petroleum diesel and also needs to be properly treated in the winter. While it functions like petroleum diesel, it also has a cloud point and when the temperature falls below that cloud, point waxy crystals begin to form and clog the fuel filter.

Biodiesel is made from animal and vegetable fats/oils. Once it crystallizes, even though the tractor is warmed up, some will still sink to the bottom of the tank and be drawn into the system where it ends up in the filter. Caught in the filter, it forms a waxy/pasty substance as shown in the photo. Our tractor has two filters in the fuel line and they are designed to filter out dust or small dirt particles, but congealed biodiesel will totally clog them shut.

I have purchased diesel from the same gas station for over 15 years, and it has always been a good-quality presenting no problems. The reason I suspected someone put some untreated biodiesel into my tank is because it was filled to the very top of the filler spout and I never fill it that full, plus it had been used a couple times since the last filling.

At first, I reasoned that no one would vandalize my tractor by putting fuel in it, so I must have slipped up in filling it and not noticed. I didn’t want to think that anyone would go to the trouble to vandalize our tractor in this manner. Because of this incident, I have learned more about diesel and biodiesel than I thought I would ever need or want to know. The vandal clearly didn’t know whether my tractor was gasoline or diesel, but untreated biodiesel added to either fuel during the winter would damage both types of fuel.

A second indicator was the fine dirt that came from the tank when it was drained. When you purchase regular petroleum-based diesel from a gas station, there will likely be a few tiny particles of dirt in it. Biodiesel actually has superior cleaning properties and will clean any sediment out of the tank. When using normal diesel, the minute solids settle to the bottom of the tank and stay there or will end up caught in the fuel filters. Mix in biodiesel and it will clean that debris from the tank bottom and flush it out.

When we drained the fuel tank, we noted some fine dirt in the bottom of the clean receptacle which had been flushed out of the tank and would have eventually ended up in the filters. That is why fuel filters need to be changed at regular intervals.

Had it not been for two very knowledgeable people who told me that it looked exactly like biodiesel that had crystallized, I would never have determined what the cause was. Clearly, we have one or more very diabolical vandals in our area. They may be much easier to catch now that we have motion sensors and a camera installed should they ever make a second attempt.

If any reader ever sees a filter resembling those shown above, it may shorten the extensive research I ended up doing to find the cause.

For more on Bruce and Carol McElmurray and remote living go McElmurray’s Mountain Retreat.

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