Solvent properties of biodiesel
Biodiesel, unlike petrol diesel, is a good cleaning agent. This is ultimately one of biodiesel’s benefits. If your car has been running on regular diesel for a long time, it may cause you some trouble initially. Most gas stations don’t filter their fuel very much, so a lot of dirt and small particles are allowed into your gas tank. As long as you are using petrol diesel, this debris will just sink to the bottom of the tank and sit there. But biodiesel, being a good solvent, will dissolve all of the old accumulated dirt out of the bottom of the tank. You will end up with a healthier, cleaner engine. But know that your vehicle’s fuel filters will then catch and trap the debris, before it reaches your engine.
If your car has been on petroleum diesel for it’s entire life – for ours it’s 130,000 miles, there is probably enough debris in your tank to clog your fuel filters at least one, if not more than once. When first making the switch to biodiesel, especially if your car is more than a couple of years old, you should expect your fuel filter to potentially clog.
There are several ways of preparing for this and avoiding trouble. One is to purchase an extra set of fuel filters, and learn how to change them yourself. Another possibility is to have your mechanic change your fuel filters, after you’ve run through your first few full tanks of biodiesel but before you experience clogging.
A clogging fuel filter will cause your car to lose power, usually in spurts or sputters, and especially in places where you try to open up the throttle more (such as going uphill), because the amount of fuel able to pass through it will be limited. If you feel your fuel filter beginning to clog, have it changed as soon as possible.
Biodiesel’s solvent properties can also flush more than just debris from tanks. If a fuel tank is rusty inside, or if it has an algae or bacteria infestation, these things will also flush out, and in this case more extreme measures should be taken. If you experience unusual or persistent fuel filter clogging even long after you’ve switched to biodiesel, or if you find red (rust), green (algae), or mucous-like (bacteria) deposits in your filters, you may need to have a mechanic remove the fuel tank and clean it. The tank can be boiled out by a radiator shop, or cleaned with a strong acid solvent and some nuts and bolts used to knock the debris loose. Algae and rust are most common in cars in coastal areas that were not used very often, or spent a long period of time sitting idle. There are also biocides and other tank-cleaning additives that could provide a cost-effective solution.
Lubricating properties of biodiesel, and ULSD warning
Biodiesel is a good lubricant, which is very good for engines, fuel-lubricated injector pumps, and any other moving parts that come into contact with the fuel. It will also tend to lubricate and expand any seals that it comes into contact with – a wonderful side benefit of using biodiesel!
Ultra-low sulfur petroleum diesel (ULSD), on the other hand, will tend to shrink and harden seals. All diesel sold in California is ULSD, due to emissions standards (our truck has used CA diesel). ULSD does have additives to improve its lubricity, but it has still been reported to cause injector pump failures for vehicles with fuel-lubricated pumps.
Switching back and forth between 100% biodiesel and ULSD can exacerbate this problem. If seals are expanded and then shrunken too many times, they may eventually become damaged and begin to leak. Going back to 100% biodiesel (B100) might (or might not) allow a leaking injector pump to re-seal. Some people suggest running some B100 through, and then allowing it to absorb for at least 24 hours before giving up and committing to an expensive injector pump repair or replacement.
The best way to avoid this problem is to avoid ever using 100% ULSD petroleum diesel in your car. If you are traveling to a place where you need to blend petroleum diesel with your diesel in order to avoid gelling (colder climates), or because you aren’t able to find biodiesel in the area, try to keep at least 25% biodiesel in your tank. Remember, biodiesel and regular diesel can be blended in any proportion, so it is no problem to fill up with regular diesel when your tank is still half full of biodiesel.
We are using biodiesel in our main tank, blended with diesel when necessary or when biodiesel isn’t available on our journey. We will update on our experience with biodiesel as we go along.