How Different Oils Influence The Gel Point Of Biodiesel

Biodiesel in the snow

Biodiesel is truly an awesome alternative fuel! However, when it gets cold outside, it tends to get thick and gel up which can cause issues with trying to use it in colder climates. Something else that’s interesting about biodiesel is that the temperature that it gels at is highly effected from the oil that it’s made out of.

A few years back, we made small batches of biodiesel from brand new canola, safflower, corn, soybean, olive, and peanut oil.
Biodiesel Made from different oils

Once we had the samples made, we placed them outside on a stand with a thermometer near by and started to see what happened as the temperatures started to drop.

One evening the temps dropped clear down to 10° F making it an ideal time to see just how the samples were doing.
Biodiesel at 10 deg F

All of the biodiesel samples had gelled up, but what was interesting to see is that some were thicker than others. The Safflower and Canola, while gelled, were still very liquid-ish. They still could move around fairly freely in the jars with very little effort. Especially the safflower oil! While it looked gelled up, in reality it moved very freely and looked more like cloudy biodiesel. The corn, olive, soybean, and peanut oil however were completely solid.

A few days later after the samples had gone through several nights of sub-freezing temperatures, the thermometer read about 40° F, so we decided to see how the samples were doing. The pictures were taken in the early morning so the samples were “warming up” from a pretty cool night.
Biodiesel at 40 deg F
The Safflower and Canola again were doing great! While they had a little cloudiness in the bottom of their jars, they were very liquid and moved very freely. The soybean and corn oil, while cloudy looking all the way through, also moved around fairly easily in the jar. The olive oil was just on the verge of starting to thaw, but was still pretty thick in the jar. The peanut oil sample was still solid as a brick!

Over the next few weeks we continued to watch the samples and snap pictures of how they were doing.
Biodiesel at different temperatures

What we discovered was pretty interesting. By far, the safflower and canola oils did the best at staying liquid at lower temperatures. The corn and soybean samples were the next best samples of the bunch. They would tend to gel when the temperature dipped into the high 30’s and would start to liquify as the temperatures would rise into the 40’s. However, the peanut oil was the stubborn one of the group. When the temps were above 50° F, it would finally start to liquify and even at 60° F a portion of it was still solid at the bottom of the jar.

The pictures below show it well…
Biodiesel At 10 deg F

Biodiesel at 18 deg F

Biodiesel at 21 deg F

Biodiesel at 22 deg F

Biodiesel at 34 deg F

Biodiesel at 30 deg F

Biodiesel at 41 deg F

Biodiesel at 45 deg F

Biodiesel at 60 deg F
Some of these pictures were taken as the temperatures were increasing (in the morning) and others were taken as the temps were falling (going into the evening), which shows that even though it may be a certain temperature outside, you have to consider how long the biodiesel has been sitting at that temperature (or if the temps are cooling down–evenings or warming up–mornings)

What’s even more interesting is just how wide the range is from one oil to another on gel points. For example, the canola & safflower based biodiesel easily were able to stay nice & liquid clear down into the 30’s, while the peanut oil went solid as a brick in the 50’s.

Another interesting point is that larger volumes of biodiesel will take longer to heat up and cool down. These were small quart size jars so the samples could fluctuate in temperature much more rapidly than say a tank full of biodiesel would sitting in your vehicle. However, it still illustrates the point that it’s important to understand the gelling properties of the biodiesel you’re using and plan ahead.

There are several ways that you can “winterize” your biodiesel. Here’s a few that we’re aware of:
1) Cold stratify your biodiesel
– Let your biodiesel get good & cold. You’ll notice a layer of liquid biodiesel will form on the top of the fuel. Draw this off and put it in a separate container for use in colder weather. The thick, solid fuel can be stored away and used in warmer temps.

2) Cold filter your biodiesel
– Same as above, except that you run the biodiesel through some sort of a filter to catch the thicker fuel. Sock filters work great for this method! The filter will act like a “cold filtration” device to remove the thicker parts of the fuel from your biodiesel. Like above, the thicker fuel that stuck to the filter can be put away for use later on when the temps are warmer.

3) Blend with diesel fuel or kerosene
– When the temps get cold out, you can blend your biodiesel with diesel fuel or even kerosene. Most people experiment with a 50/50 mix of bio to petro diesel and then work from there to identify the right blend ratio. Remember, as seen above, different kinds of oil can gel at different temps, so there’s not a hard & fast rule on what blend you should go with. For example, it will require less diesel fuel or kerosene to “cold treat” a gallon of canola based biodiesel than it would say to treat a gallon of soybean or peanut based biodiesel. So, grab yourself some quart jars, mix up some samples and do some tests to see what blend ratio works the best.

If you have to error, always error on the side of blending in more diesel or kerosene than may be required to keep the biodiesel at a liquid state. The reason for this is that if you misjudge and get gelled up on the side of the road, you may be there for a while and no one likes freezing their kiester off in a cold car on the side of the road.

4) Use fuel filter heaters or heat exchangers

– If you’d like a little more “insurance” against gelling, you can also install fuel filter heaters or heat exchangers to keep your fuel nice & toasty warm! We offer fuel filter heaters in electric & coolant heated models and carry a stainless steel tube in tube heat exchanger and two awesome flat plate heat exchangers that work extremely well!

Biodiesel Anti-gel Additives
Just a note about biodiesel gel point additives. Don’t waste your money. They don’t work very well at all! As of this writing (Nov. 2014), there aren’t any truly “good” anti-gel additives for biodiesel available on the market.

Several studies have been performed by several universities and organizations trying to find the ideal cold flow additive for biodiesel. So far, all the studies have shown that of the anti-gel additives available, none of them truly will keep your fuel from gelling. (Check out this study on just how poorly they work!) Some may slow it down a bit, but none that we’re aware of will truly keep it from gelling up on you in the cold.

We’ve performed tests with Amsoil’s Cold Flow Improver and found it to work marginally well and have heard “ok” things about Technol’s B100 Biodiesel Cold Flow Improver, but nothing has managed to stop biodiesel from gelling completely. When people call in and ask what the best anti-gel additive is, I still tell them diesel fuel & kerosene. It’s also the cheapest too!

So, in conclusion, if you’re planning on on using biodiesel in colder weather, get to know it’s gel point and do some testing to see what blend of diesel fuel to biodiesel works best to keep your fuel nice & liquid. It is possible to use biodiesel year round, but it definitely takes some knowledge of what your gel point is so that you can control it.

Also, if you’d like several tips & tricks on using biodiesel when it’s cold out, be sure to check out our great article on how to do it successfully!
Running Biodiesel In The Cold

Additional Resources
WVO Designs awesome article on oil gelling temps – They have some great tables on the different cloud points and pour points of different types of Biodiesel.
VegBurner’s great oil properties article! – Includes some awesome gel point tables!

About Utah Biodiesel Supply

Utah Biodiesel Supply is an industry leader in offering innovative ways to empower our customers to produce Biodiesel. From free online instructional videos on how to get started making this great renewable fuel to promotional items to help our customers proclaim their energy independence, Utah Biodiesel Supply has it covered. With the widest selection available of Biodiesel equipment, supplies, and promotional items, you're sure to learn something new about Biodiesel every time you visit.

4 comments on “How Different Oils Influence The Gel Point Of Biodiesel

    • I had an old Isuzu that mentioned adding gasoline to the fuel as an anti-gel additive several years back, but I’ve never attempted it with Biodiesel. Not sure how the newer diesels would fair with gasoline in the fuel. Kerosene or regular diesel fuel though has always worked well for us.

    • While this might work great in lower-pressure fuel systems (like UBS poster’s old Isuzu) in modern high-pressure common-rail systems this can be potentially disastrous. Pressurizing gasoline up to 25,000 PSI is not a good idea, no matter how dilute!

  1. Pingback: Gelled again!! Third time.... - Page 2 - Dodge Cummins Diesel Forum

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