Biodiesel degrades natural rubber hoses found in some older engines, and those hoses must be upgraded to Viton. All biofuel systems need to be periodically monitored for long term hose degradation. Understand that most liquid products have volatile esters, or aromatic compounds, that get absorbed by all the seals, gaskets and hoses. Conversion to biodiesel requires a slow changeover utilizing slowly increasing percentages of biodiesel. The older your car, the slower the changeover needs to be. Sudden and complete change is very likely to lead to shrinking seals and leakage, as well as hose degradation. As a loose rule, if the diesel fuel system components have more than 15 years or 150,000 miles, the change over is not likely to be successful, expect leakage and seal failure. To use biodiesel successfully, perhaps those hoses and pump seals should be replaced first.
Biodiesel has a cloud point well above regular diesel fuel. Crystals start to grow and the fuel will not flow through filters, eventually it actually freezes. Regular diesel clouds at 0 F. Biodiesel cloud point varies according to its seed oil and its water content. Some Canola based fuels cloud at 14 F, whereas a tallow based fuel could cloud at 60 F. Local biodiesel clouds around 32 F when it is fresh. For Bay Area biodiesel, dilution with 50% regular diesel for winter trips to Tahoe is required, although Bay Area usage is well within its usable range. Once a diesel engine is running and warmed up, fuel heated by the motor returns to a reservoir in the tank, allowing colder weather and altitude changes. More information on this topic is available in the individual Karmakanix web pages on the different diesel motors.
For those who regularly travel long distances, there are two different forms of action. First is to carry car boys, or tanks of biofuel sufficient to cover the trip. Those tanks must be fresh fuel. You don’t have to be a math major to understand how to progressively dilute the biodiesel with petroleum diesel. The idea is to keep at least 25% biodiesel in your tank at all times. The other tactic is to use biodiesel successfully in the winter is to consistently use a blend of biodiesel and regular diesel. Understand that the issue is that all the seals and gaskets in any system absorb the volatile esters, or aromatic compounds, of the liquid to which they are exposed. Changing from pure biodiesel to pure petroleum diesel is quite likely to cause seals to shrink, degrade and fail.
Use biodiesel manufactured by certified and high quality sources. We have been linked to the Biofuel Oasis for this entire century, and can vouch for their consistent efforts to monitor and maintain the quality of their fuel. Check out the Biofuel Oasis website for more information. They also have links to other quality biodiesel sources around the Bay Area. They are the key to how most of our customers use biodiesel successfully.
Drive a lot, or don’t fill up all the way! To translate, remember that biodiesel degrades over time through oxidation and chemical reactions due to water content. Do not let your fuel get more than two months old, and consider the residual fuel in your tank for overall age. If possible, and as feasible, run your tank fairly low before you fill up. Those customers who use biodiesel successfully tend to drive 1000 miles or more each month. This seems to avoid repairs and problems. Those who drive less than 200 miles a month seem to be the targets for contamination, clogs and leakage. Low mileage owners and those who leave their cars for a couple months without driving them should constantly use stabilizing additives with every fillup.
Do NOT use additives unless you are sure they are compatible with your biofuel. Certain additives contain methanol or acids that can wreck your fuel system in a few miles. Redline, Stanadyne, Amsoil are definitely compatible with biodiesel. Many other diesel fuel additive manufacturers exist, and many of them may be safe to use with diesel, but we only have experience with those 3 brands for biodiesel additive. Amsoil and Stanadyne are not easily available. Here is a link to O’Reilly’s Auto Parts for the Redline stuff.
Be careful when filling your tank or changing your fuel filter. Long term exposure of biodiesel on paint can degrade your paint job. Typically, we only see this problem right under the fuel door. If you slosh when you fill, clean it promptly with just soap and water.
Common Rail Diesel Tdi: CR = NO CAN DO!
Please understand and accept that biodiesel should NOT be used in the modern common rail diesel systems manufactured 2007.5 and later. This includes the Touareg V-10 Tdi starting in 2005, as that was the year they got a Diesel Particulate Filter. The emission control devices and their function prohibit biodiesel usage due to oil contamination resulting from the regeneration cycles. Alternative information exists that says you can use biodiesel in a common rail system if you change the oil every 3000 miles, thus preventing long term contamination of the oil. We have seen issues other than oil contamination in CR Tdi cars that used to run biodiesel, like a failed exhaust pressure sensor. VW and Audi will NOT honor ANY warranty on your Tdi in the case of engine failure or any fuel system related failure if you have been using biodiesel at ratios over 5%, or BD 5.
It is not the policy of Karmakanix to discourage biodiesel useage. But we feel that your average Tdi customer who really wants to run biodiesel in his CR Tdi should wait until well past 120,000 miles, so as not to void any existing factory warranty. There is the absolute necessity to slowly change from regular diesel to biodiesel progressively to avoid leakage. Understand that biodiesel is not going to work well for Diesel Particulate Filter regeneration, and so it is wise not to just use your car for around town, low-speed driving. Consider running a blend like BD 20. That will help avoid leakage issues, help with DPF regeneration, and allow you to safely transition to regular diesel for long distance driving without incurring leakage issues. Please feel free to call our Service Advisors for more technical support.