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Colorado Biodiesel guide to
handling emergency biodiesel gelling problems

When a sudden front of cold weather sets in and your current biodiesel blend is suspected to be too high for the temperature drop, the following can be used as an "emergency guideline" to help avoid biodiesel-related gelling problems.

First, for EVERYONE: If you have a block heater USE IT!

Second, DO NOT, repeat DO NOT use starting fluid on ANY diesel that has working glow plugs. Period.

If you know your glow plugs are not working and you feel you must use a "fluid spray" to help get the engine to run (if it turns over with the starter but will not "fire"), use WD40 (it is a flammable oil, unlike starting fluid which is an EXPLOSIVE!) or another flammable oil in spray form sprayed into the air intake.

If you're not normally prone to gelling:

1) Get some diesel or kerosene in your tank ASAP. Run your engine for a while to get the diesel mixed with your bio blend (independant of blend ratio)

2) Procure some Diesel 911* for your trunk because you'll eventually be in the next class of people:

If you ARE prone to gelling, but are still running:

1) Get some Arctic Express* (white or blue bottle) and add DOUBLE the label amount to your tank when topping up with diesel #2. Whatever concentration of bio you have, in extreme cold or the threat of extreme cold temps, top it up with petroleum diesel (until we've come up with a "green" solution to the high CFPP and gelling problems of Biodiesel, we'll have to use "some" petroleum when in extreme cold climates to keep running.)

2) Procure some Diesel 911 for your trunk.

If you are gelled and cannot start (this means it's directly because of cold temps, not some other engine issue):

1) Remove your filter (spin-on or canister, not just the secondary in-line filter) if you know how and use a new filter (if you have one handy - save the old one, it'll be fine when it thaws), if you don't have a new filter handy, empty the fuel out of the old one as best you can (heat and drain if possible) and COMPLETELY FILL the filter with either; Power Service® "Diesel Fuel Supplement", "Arctic Express" or "Diesel 911" (best choice), replace filter. Use 1/2 bottle of Diesel 911 in the tank and top with diesel #2.

2) If your secondary (usually a clear plastic in-line filter) is gelled to solid, you'll have to remove and replace with another one or place it in a warm place. Also, if that is a wax candle (plugged with solidified fuel), you'll need to place a space heater under the car or some other heat source as the fuel in the lines will also be solid!)

3) Make sure your battery is fully charged AFTER performing steps 1 and 2 above and attempt to start the car (sometimes in extreme cold, you will need to go through two glow cycles before attempting a start - do not run the starter for more than about 30 seconds at a time!)

4) If the vehicle still will not start after; plugging in for at least 3 hours, charging battery, filling filter with supplements and adding D1 or D2 to the tank, you'll have to heat the car in some way (covering your car with a car cover or tarp and placing a 100w light bulb -that has 110v and is on- in the engine compartment overnight sometimes works, but a warm garage is best if available.)

With very cold weather (below 10 F), what I'd suggest as a fail-safe blend is an ASTM B20 with "Arctic Express" added to the tank at DOUBLE the suggested ratio for D2 and keep some Diesel 911 in your trunk.

Many factory manuals suggest up to 30% regular gasoline (RUG) as an antigell in very extreme cold temps. I've used about a 10% RUG blend with home-brewed/WVO bio, but due to the volatile nature of gasoline and the damage it can cause to injection systems in diesels, I would only suggest extreme caution if you plan to use this as an antigel.

If you can afford it, I'd suggest keeping a 5 gal jug of kerosene handy as insurance against freeze-ups. If the weather is predicted to be extreme cold, mix the kerosene in with your fuel BEFORE the temps get below about 40 degrees (for best blend.) DO NOT use more than 50% kero in your tank though (kerosene does not have good lubricating properties and can damage the IP with long-term use.)

Disclaimer: The above guidelines are by no means complete or definitive. They were learned from years of experience and customer experience. I am in no way connected with Power Service® nor do I gain squat by endorsing them, but have found their products to be the most efficacious for diesel service (freezer tests, field tests, etc.)

Tip from "Girl Mark": Test your own biodiesel to make sure you know what its cold flow properties are in your regional climatic conditions. (Below you can find some tips on doing your own freezer testing of fuel.)

*"Arctic Express" and "Diesel 911" are both trademarked products by Power Service® Corporation.


1) Get a refrigerator thermometer (I use a calibrated digital, but the cheapo metal ones as shown in the forum pics works fine)

2) "Calibrate" your freezer; adjust the temp control until you get a fixed baseline temp (aka; 0 degrees, 10 degrees, 20 degrees, etc.), this can take a bit as you have to adjust, let the temp normalize (4-6 hours) then re-check your thermometer, re-adjust, etc.

3) Once your freezer is "calibrated" at a fixed temp (usually the lowest temps you'll commonly see in your climate), you can start testing samples:

- Place a fixed quantity (don't use too little, probably 40-50ml is min) of your biodiesel or blend in a clean sample jar with a tight lid and place on the freezer rack in an area that is cleared of food or other material at least 6" on all sides. Let this stand in freezer till temp normalizes and add at least 4 hours.

- Check your sample after it has been at the baseline temp for at least 4 hours (overnight is good)


- First test your biodiesel in the refrigerator (38-45 degrees) to see if it gels or has particulates in it.

- Just because your homebrew biodiesel gels at 33 degrees, it doesn't mean it's "Bad" fuel. Feedstock plays a heavy role here!

- Use the same sample size for ALL your samples. Always use clean jars. Write down the quantity of blend or winterizer you're trying and re-test all samples if positive or negative results are had.

- Make sure any tests you perform are repeatable by a third party.

- Send me info on your results if you find something seemingly groundbreaking, I will make sure to disseminate this info over the community.

(these are my own, for the layman)

GELLING: Fuel "thickening" due to wax crystal "clumping" from extreme cold temps (the "winterizers" and "antigels" only modify the way the wax crystal interact -to keep them from "clumping together"-, they do NOT "melt" the wax or reform it into a liquid, only heat can do that, so using too much antigel will do no good once you've reached a saturation point in the fuel.)

CFPP: Cold filter plugging point - the point at which wax crystals will effectively reduce fuel flow through a filter (Kerosene is more refined than D2 -diesel-, so it has less wax -parrafins- and a lower gel and CFPP.) From Iowa state: "The cloud point is the highest temperature used for characterizing cold flow and the pour point is the lowest."

CLOUD POINT: The point at which wax crystals start to form and the fuel visibly "appears" cloudy (due to temperature, NOT from other contaminants) - ~10-15 degrees in D2.

POUR POINT: Technically, this is the "lowest temperature at which movement of the fuel sample can be determined when the sample container is tilted", ie; it's the coldest temp that a fuel can still be "liquid" at.

Click here for a table of pour point for diesel fuel by state in the US
thanks to TDIclub!

CWBUIF: This is a complex time/temperature formula that can be translated as follows: The amount of time that the weather sustains extreme cold temps and drives a normal, rational biodiesel user insane (Cold Weather Biodiesel User Insanity Formula.)

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