Article Donated by troy from infopop

When you speak of winter treatment of biodiesel, you have entered the dark arts.

I say that because your homebrew can be subtly or dramatically different than mine, your vehicle can be more or less tolerant of some wax precipitate, and your weather can certainly be different than mine. The following discussion assumes you are making top quality, well converted, properly washed, dried and filtered biodiesel. You've done quality checks like the 3/27 test, etc. If you are cutting corners on any of that, you can get stranded and freeze your genitals off. You've been warned.

Despite all that, here are some general guidelines:

A. Your starting oil matters. Unhydrogenated canola is generally considered to make the best winter biodiesel. Soy is pretty good. Animal fats, coconut oil and palm oil are terrible winter stocks. The resultant biodiesel gels in the temp range of 40-70F. Partially hydrogenated oils (shortening, often a semi-liquid) can give anything from good to terrible winter performance. Fully hydrogenated veggie oils (even canola) make lousy winter fuel. These oils are solid at room temperature.

B. Blending with winterized petro diesel works, kerosene works even better. The colder it gets, the more diesel or kero you need. I'll post some data from Duffscience later that shows how much petro diesel or kerosene it takes to attain a certain gel temp. There's also a link with a nifty calculator to estimate how much K-1 you need.

C. Additives. None of the diesel additives for winter work as well in biodiesel as they do in petro diesel. Some additives help reasonably well if you double the recommended rate. Triple rate doesn't seem to bring any additional benefit, and the current thinking is that these additives mostly work on the petro portion of your winter blend, and not so much on the biodiesel itself. This can get fairly expensive. There is a lot of research going on right now to find the holy grail additive that will relieve us of the need to mix petro. So far as I know (September, 2006) it doesn't exist yet.

Here's a recent link from Graydon showing some research done at the University of Idaho on winterizing additives:

http://www.uidaho.edu/bioenergy/NewsReleases/TechNote3.pdf

Whatever scheme you decide on, be certain to do your own freezer testing to find out how your blend works. You should measure cloud temp (the temp at which the biodiesel starts to get wispy cloudy stuff (wax crystals coming out of solution)) and gel temp, the temp at which the biodiesel no longer behaves as a liquid when you tilt your container on its side. You can drive, for a time, with cloudy fuel. But eventually the wax crystals will plug your fuel filter and you will be walking. Once the fuel gels, you are totally beat. Cloud temp is usually just a couple of degrees above gel temp.

Oh yeah, and if your fuel clouds at 30F overnight, you might discover that it clouds at 37 F if you chill it/check it for a few days. Same with gel temps. An "overnight" reading of 17°F is no guarantee that it won't gel at 8 or 10 degrees (F) higher if you chill it for a week. Did I mention that this is a black art?

Here's what I do, which is a combination of blending with K-1, additives and cold processing to take the high temp waxes out.

1: Mix your washed/dried Biodiesel with some percentage of kerosene. I typically add enough kerosene to make true B-66. Do the mixing warm if at all possible and mix it well. By warm, I mean more than 60F.

2. Add 2x the recommended amount of Power Service DFS (Diesel Fuel Supplement) cetane improver. This comes in a white bottle and is available at most Wal-Marts and just about any truck stop. Mix well. Some sources say this step must be done at warm temperatures (like around 60F) to be maximally effective.

3. Cold processing. That's where you "refrigerate" your mix for a few days (which in my case usually means leaving it outside for a few days) and then siphoning out the liquid portion the next day and leaving the crystallized sludge portion for summer use. If I don't get 3 days of good cold weather, I throw a couple of cubies in the freezer for 24 hours. A longer chill period is much more effective than a short one. It's amazing how much more junk precipitates after a full day in the freezer compared with just overnight. Then I let it warm up a bit to clarify the liquid fuel and really settle the waxes. This improves yields a little. Make sure you do this so you can go right to the siphoning step without disturbing the jug. Siphon the clear stuff out and you're good to go. The finished product of course is no longer B-66, but something less than that, depending on 27 different things.

I use a siphon with a "J" shaped bend on the end that I made out of 2 copper 90's. It makes it much easier to siphon from the top down and not disturb the waxy sludge on the bottom. The colder you chill the mix, the better the anti-gel performance in cold temps, and the lower your yield. Interestingly, the precipitated sludge has more BTU's per liter, so you may notice slightly reduced performance on the winter blend. The "sludge" makes great summer fuel.

That's it for the fuel. Of course, there are other factors as well:

1. My car always sits in a garage overnight, along with my wife's car. This helps retain heat. Perhaps your car is exposed to the full fury of winter temps overnight.

2. I added a 120V coolant heater to my VW and use it religiously at or below freezing. So my engine does not start off stone cold in the morning. This increases under-hood temperatures and also makes my heater work right away, which is a nice bonus.

3. TDI engines like mine use a continuous fuel loop, so excess fuel (which is hot) gets returned to the tank. If it's cold out, it routes that hot fuel through the fuel filter canister. If your diesel doesn't do that, you could have a problem with wax crystals plugging the filter.

4. I have a Neoteric brand 12V fuel line heater activated by a rocker switch on the dash. This is in the fuel line just prior to the fuel filter.

5. Never fill the tank right full, so if you have a sudden -20F cold snap, you could dump a bunch of kerosene or winterized diesel in there, along with some more anti-gel additive. You'd at least stand a chance then.

6. I keep a quart jar of winter blend fuel outside on the way to the garage. That gives me a visual check of what's going on in the tank.

7. In some previous model years, they had a problematic fuel pickup in the tank that would plug with even trivial amounts of crystallization in the fuel. The newer design eliminates that problem. Who knows what your pickup looks like.

I am thinking about setting up a coolant loop to heat the fuel tank, like the SVO folks do. (I have since discarded this notion, since my formula has been 100% successful the last two winters.) Legal Eagle is seriously considering setting up a two tank system with heated fuel tank, fuel lines and fuel filter. That would be the cat's meow. Ask him about it.

Please note that you should mix your blend for worst case scenario temperatures plus a fudge factor of several degrees. You should not look at the forecast for tomorrow and mix your blend for that exact temperature. Or maybe you like living on the edge???

Here's the charts and links I promised:

Try this newer link (good as of 2/1/07): http://www.duffscience.com/bd_calculators.htm

The following numbers are all based on mixes with biodiesel made from new soy oil. YMMV

Please note that there is a whole other vibrant informative discussion about winter issues over here: http://biodieselnow.com

Finest regards,

troy