Biodiesel Report: What B20 Means to You and Your Warranty

By Dan Collins on 23 October 2012
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Five years ago, biodiesel was a form of fuel that the diesel enthusiast would convert his or her vehicle to use.  Since then, it has been forced into the mainstream through various government mandates and subsidies, in the form of blended fuels that are often the only option for drivers of diesel vehicles. Although biodiesel has the potential to reduce both dependence on foreign oil and fossil fuels, its premature introduction into everyone’s fuel tanks, and especially the inconsistency of the biodiesel and the amount of it being mixed in are starting to cause problems.

Ethanol is perhaps the most well-known biofuel and has been added to almost all gasoline in the U.S. for some time now. . Biodiesel is fuel that is created from natural oils, fats, and greases and, unlike ethanol (which is far different and less efficient than gasoline), is a closer match to the diesel we’re used to. In theory, diesel engines require little modification to burn it. However, modern diesel engines are being challenged by an ever-increasing amount of biodiesel content and both carmakers and diesel passenger car owners are nervous about the future.

Currently, several states in the U.S. have begun to support mandates that call for the use of biofuels, even though the renewable fuel’s varying and largely unreliable quality means trouble when it is used in passenger cars’ diesel engines, since they are finely tuned to meet higher emissions standards than diesel powered trucks and farm vehicles do.

This problem has been particularly acute in Illinois, where any diesel fuel with more than 10% biodiesel content is exempt from state tax.  As a result, almost all filling stations sell diesel with higher biodiesel content, generally B20 (20% biodiesel content).

Last month, acting under the Energy Policy Act of 2005, the U.S. Environmental Protection Agency (EPA) increased the mandate for oil refiners to create biodiesel by 28%.  The mandate for 2012 was 1 billion gallons; this puts the 2013 requirement at 1.28 billion gallons.

The EPA’s move “is another step that strengthens America’s energy security by reducing dependence on foreign oil,” said EPA administrator Lisa P. Jackson.

The United States’ Renewable Fuel Strategy policy, however, has also been the subject of a certain amount of controversy.  In August, the United Nations called on the U.S. to halt the policy as a measure to avert a global food crisis.  The United Nations Food and Agriculture Organization predicts that the impact of the drought currently impacting much of the country, in conjunction with the RFS’ earmark for 40% of corn product to be used for fuel production will contribute to a global food crisis, the 26% increase in corn prices from June to July notwithstanding.


Modern diesel passenger cars currently being offered in the U.S. were designed to use B5, or 5% biodiesel content; as a consequence, using blends with as much as 20% biodiesel have caused problems ranging from check engine warnings to reduced fuel economy and outright engine failure. In addition, the manufacturers’ warranties on these cars support the use of only up to B5, which was the biodiesel standard when the cars were engineered to meet U.S. and especially California Emissions standards. The move towards higher biodiesel content fuel has the unfortunate side effect of, putting the consumer on the hook for the cost of repairs which can be rather expensive.

All manufacturers of passenger cars available with diesel engines in the U.S. support the same B5 standard, while heavy trucks and other diesel machinery generally support a B20, and some even endorse 100% biodiesel content. Despite the move to B20 in some areas, the manufacturers are largely holding their ground.

The five manufacturers that offer passenger car diesels in the U.S., Audi, BMW, Mercedes-Benz, Porsche, and Volkswagen continue to maintain that B5 is their recommended blend.  Given the move towards greater biodiesel content, all of the manufacturers are not only concerned but currently studying the long-term effects of the newer blends on their engines. A statement in a Mercedes-Benz Biodiesel Information publication makes the automaker’s position crystal clear: “Diesel fuels containing a higher percentage of biodiesel, (e.g. B6 to B20) according to ASTM D7467 as well as straight biodiesel (B100/100%) ASTM D6751 may cause severe damage to your engine/fuel system and are not approved.”  In case there are any lingering doubts, one need only read the last page: “Any damages caused by the use of such non-approved fuels will not be covered by the Mercedes-Benz Limited Warranty.”

Click here to continue to Page 2Biodiesel Quality Standards, the State of Illinois, What Can Go Wrong

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