Engine oil formulations for biodiesel fuels

#The disclosed technology relates to lubricants for internal combustion engine, particularly those fueled with biodiesel fuels.

#Biodiesel is a general term for fuel-grade materials derived from natural sources such as vegetable oils. They are often fatty acid methyl esters (“FAME”) such as rapeseed methyl ester (“RME”) or soya methyl ester (“SME”). Biodiesel fuels are becoming more prevalent for fueling of diesel engines. The increased use of diesel passenger vehicles in Europe and elsewhere is in part a cause of this increase. Current European diesel standard (EN 590) allows for 5% biodiesel component to be incorporated into fuels, which will soon rise to 7%, with indications that 10% biodiesel content will be introduced by 2012.

#Simultaneously, there is continued pressure for reducing particulate matter emissions from diesel engines. Euro 5 requirements, scheduled for implementation in 2009, require reduction in particulate matter to 0.05 g/km. Such levels can only be attained, practically, by use of a diesel particulate filter. These filters require regeneration once they are full of soot, and this is typically achieved by increasing the filter temperature to burn off the soot. The temperature increase is often achieved by post-injection of fuel into the engine cylinder.

#Various preferred features and embodiments will be described below by way of non-limiting illustration.

#The lubricant as described herein is particularly useful for lubricating diesel engines that are fueled with a liquid fuel that comprises a biodiesel fuel, that is, that contains a certain amount, e.g., at least 2 percent by weight, of a C1-C3 or C1-C4 alkyl ester of a carboxylic acid of 12 to 24 carbon atoms. Such alkyl groups may include methyl, ethyl, 1-propyl, 2-propyl, n-butyl, sec-butyl, isobutyl, or tert-butyl. When the alkyl group is C1-C3, the groups may be methyl, ethyl, 1-propyl, or 2-propyl. In certain embodiments the alkyl group is methyl or ethyl, or alternatively, methyl. The amount of such ester in the liquid fuel may be 2 to 100% by weight, or 4 to 100% or 5 to 100% or 10 to 100%, for instance, 4 to 12% or 5 to 10% or generally 2, 4, 5, 10 or 12% up to 100 or 90 or 80 or 50 or 30%. These percentages are normally calculated on the basis of the liquid fuel excluding any performance additives that may be present. The balance of the fuel may be a petroleum-derived fuel or fraction, such as a middle distillate fuel or other petroleum fuel conventionally used to fuel a diesel engine. The amount of sulfur in the fuel may be less than 300 parts per million by weight for low sulfur fuels, or less than 50 ppm or less than 10 ppm, e.g., 1 to 10 ppm S for ultra-low sulfur fuels. Fuels may also contain higher levels of sulfur, such as up to 1000 ppm or 300 to 500 ppm. Any sulfur which is present may come from the biodiesel component or from a petroleum fraction.

#Biodiesel fuels can be derived from animal fats and/or vegetable oils to include biomass sources such as plant seeds as described in U.S. Pat. No. 6,166,231. The esters may thus include, as described above, methyl, ethyl, propyl, or isopropyl esters. The carboxylic acids may be derived from natural or synthetic sources and may contain a relatively pure or single component of acid in terms of chain length, branching, and the like, or they may be mixtures of acids characteristic of acids obtained from animal or, especially, vegetable sources.