Nope, a source I used to have dumped the grill grease in with the fryer oil. It makes GREAT biodiesel, but the bio will gel at 50F. You have to be really careful about not mixing up your finished product.

Even when running a blend, sometimes you get a cold snap right after some warm weather in the spring. It happened to me this spring. That is why I added the heater. I thought winter was over, added some filtered engine oil, WVO, RUG, and Diesel to the tank. The next week it snowed. Now I have the option of plugging in my fuel tank heater in addition to the normal block heater on the engine. I also added a 60 watt battery heater. The battery is in the trunk on W140s so it indirectly helps to heat the fuel tank also.

Jim

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1995 S350D, Green with black leather interior.
Bought January 2008 w/ 233,xxx miles.
I did 22,000 miles during the first year of ownership.