Issues With 100 Percent Biodiesel
When fueling stations deal with pure biodiesel rather than petroleum-biodiesel blends, they must treat it a bit differently from other fuels. Because pure biodiesel is made with vegetable-based products, storage temperature it is more critical than with petroleum diesel. If biodiesel sits in a warm storage tank for too long, it can grow mold, and if it is stored at too cold a temperature, it will thicken and could be difficult to dispense.
While these problems can also occur after the biodiesel has been pumped into a vehicle, it is more important for diesel vehicle owners to watch for signs of clogs in fuel filters and systems — particularly when biodiesel is first introduced to a vehicle's fuel system and especially if the owner is using pure biodiesel. All biodiesel acts as a solvent, meaning it can loosen deposits that are stuck in fuel lines and in the fuel tank, which can then clog fuel filters, injectors and other parts of the fuel system. Experts say that this is a greater issue when pure biodiesel is used with older diesel vehicles. Higher mileage generally means greater deposits. It's also an issue with vehicles using the newest high-pressure fuel-injection technology.
Because these issues relate mainly to pure biodiesel, it might seem that the risks would be significantly less or perhaps even negligible with low-biodiesel blends.
This isn't the case, however, as the risk depends largely on the quality of the biodiesel produced. The Worldwide Fuel Charter, a list of fuel requirements endorsed by auto and engine manufacturers, only recommends the use of biodiesel blends of up to 5 percent in the United States.
"While the quality of various biodiesel blends has improved in recent years, the lack of industry quality standards for biodiesel remains a concern for us," says Darryll Harrison, a spokesman for Volkswagen of America. Volkswagen is the leading seller of diesel-fueled passenger vehicles in the U.S.
"We do believe that there is a future for advanced biodiesel and renewable diesel fuels as quality improves and the technology continues to advance," says Harrison. "In fact, our research into the next generation of clean diesel continues to ramp up as partnerships with renewable diesel innovators like Solazyme and Amryis have helped VW to better understand the impacts advanced biodiesel blends have on existing TDI Clean Diesel technology."
Still, VW is in the majority when it comes to warranty coverage of issues due to fuel use in its diesels. No automaker recommends the use of biodiesel in quantities higher than B5 for passenger vehicles in the U.S. — with one notable exception: The General Motors warranty covers use of biodiesel blends of up to B20 in the new diesel-powered 2014 Chevrolet Cruze TD.
Chrysler, Ford and GM do allow the use of B20 in some heavy-duty vans and in their heavy-duty pickups. For Ford and GM, however, that only applies to model-year 2011 and newer vehicles.