What You Should Know About Biodiesel and the Advantages and Disadvantages

Manufactured from vegetable oil, recycled restaurant oils or animal fats, biodiesel is safe, biodegradable and produces fewer pollutants than petroleum-based diesel fuel. It can be converted and used in its purest form or can be combined with petroleum diesel. There are both advantages and disadvantages of using biodiesel.


  • More expensive
  • Most automakers have not approved all blends
  • Lower power and fuel economy
  • Concerns about its impact on the durability of engines
  • In some cases, an increase in nitrogen oxide emissions


  • Produced domestically from renewable, non-petroleum resources
  • Can be used in most diesel engines
  • Less pollution
  • Less greenhouse gas emissions
  • Non-toxic
  • Safer than traditional diesel
  • Biodegradable

Biodiesel Blends

Biodiesel can be blended into many different concentrations and used in several different vehicles. B20 is the most commonly used blend in the United States.

  • B100 – Pure biodiesel – used in some farm equipment
  • B20 – 80 percent petroleum diesel/20 percent biodiesel – very few vehicle manufactures approve this blend for use in their vehicles.
  • B5 – 95 percent petroleum diesel/5 percent biodiesel – most vehicle manufacturers approve blends up to B5 for use in their vehicles.
  • B2 – 98 percent petroleum diesel/2 percent biodiesel

How well does Biodiesel Work?

Engines that operate on a B20 mixture feature similar consumption of fuel, torque and horsepower to engines running on traditional diesel. The energy content of B20 is comparable to number one and number two diesel.

Cold Weather Usage

Biodiesels cold-flow depends on the amount of biodiesel in the blend. The lower the percentage of biodiesel, the better it will perform in cold, winter weather. Number 2 diesel and B5 perform approximately the same during cold weather months. Both feature compounds that crystallize when temperatures are very low. For the best cold weather performance, drivers should use a B20 blend made with number two diesel designed specifically for cold weather.

Cleanliness of Biodiesel

The use of biodiesel substantially reduces the emission of pollutants that affect air quality. B100 provides the greatest reduction in emissions although lower-level blends will also offer benefits. B20 has been shown to reduce particulate matter emissions by 10 percent, carbon monoxide emissions by 11 percent and unburned hydrocarbons by 21 percent.

Straight Vegetable Oil

Using straight vegetable oil is illegal. It does not meet the biodiesel fuel specifications or quality standards.

Biodiesel Standards

Biodiesel used in these blends must meet specification D6751, which is a quality standard set by ASTM International. When it meets this standard, it is legally registered as a fuel or additive with the United States Environmental Protection Agency (EPA).

Blends that contain 5 percent or less biodiesel must meet the same fuel quality specifications as regular diesel fuel according to ASTM D975. Blends that contain between six and 20 percent biodiesel must meet the requirements of ASTM D7467.

Long-Term Effects of Biodiesel on the Engine

Biodiesel actually has a solvent effect. It cleans the fuel system and it could even clean off deposits that have accumulated from traditional diesel fuel use. When you begin using biodiesel, you may have to change your fuel filter as these deposits may clog it.

Studies that have been done with B20 and lower blends have demonstrated no long-term negative effects on diesel engines. Higher-level blends can have a negative impact on components of the fuel system, primarily hoses and seals.


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