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Vehicle manufacturers have developed new vehicle and diesel engine technologies compatible with B6-B20 biodiesel blends meeting ASTM D7467, “Standard Specification for Diesel Fuel Oil, Biodiesel Blend (B6 to B20).” However, recent U.S. market place fuel surveys have shown that many retail biodiesel samples are out of specification. A vehicle designed to use biodiesel blends is likely to encounter occasional use of poor quality biodiesel fuel; and therefore understanding the effects of bad marketplace biodiesel fuels on engine and fuel system performance is critical to develop durable automotive technologies. The results presented herein are from vehicle evaluation studies with both on-specification and off-specification bio-based fuels. These studies focused on the performance of fuel injection equipment, engine, engine oil, emissions and emissions system durability.

Biodiesel, a fuel comprised of mono-alkyl esters of long-chain fatty acids also known as Fatty Acid Methyl Esters(FAME), derived from vegetable oils or animal fats, has become an important commercial marketplace automotive fuel in the United States (US) and around the world over last few years. FAME biodiesels have many chemical and physical property differences compared to conventional petroleum based diesel fuels. Also, the properties of biodiesel vary based on the feedstock chosen for biodiesel production. One of the key differences between petroleum diesel fuels and biodiesel is the energy content. The energy content, or heating value, is an important property of motor fuel, since it directly affects the vehicle fuel economy. While the energy content can be measured by combustion of the fuel in a bomb calorimeter, this analytical laboratory testing is time consuming and expensive.

Biodiesel use is increasing around the world. Vehicle failures due to filter clogging issues have been reported in the field with use of biodiesel blended fuels in winter months. In certain instances, filter clogging was caused by precipitate formation above the cloud point of the fuel. Minor contaminants in biodiesel such as sterol glucosides and saturated monoglycerides are suspected to cause precipitation above the cloud point. ASTM has added a requirement to test biodiesel fuel for cold soak filtration test to prevent occurrences of this phenomenon of precipitation above the cloud point. This study focuses on understanding the correlation between cold soak filtration test results and presence of contaminants such as sterol glucosides and saturated monoglycerides in biodiesel fuels. Test samples were also subjected to thermal cycling at temperatures below the cloud point of fuel to co-correlate the cold soak filtration test results to visual observation of precipitate formation.