The trend toward low environmental impact diesel fuel has resulted in new formulations that not only benefit the environment, but that can enhance diesel engine performance as well. The sulfur content of highway diesel fuel has been reduced to a maximum of 0.05 wt % nationwide. California has an additional requirement of a maximum of 10% aromatics content which covers most highway and nonhighway vehicles. However, fuels with higher aromatics levels can be certified if they demonstrate equivalent emissions.
The introduction of these new fuels, coupled with the rapid changes in engine design to meet new emission regulations, has created the need to evaluate a number of fuel properties to ensure proper performance while protecting certain engine components (1)*. Diesel fuel lubricity and its effect on some fuel injection system equipment, such as rotary distributor pumps, is one such issue which is being investigated by a number of groups.
Many fuel additive suppliers have introduced diesel fuel lubricity additives for fuel producers who may need to improve the lubricity of their fuels. The U.S. Army Modified Ball-on-Cylinder Lubricity Evaluator (BOCLE) test method, as well as the standard version of this test, were used to evaluate the performance of several fuels and several additives at two concentrations. Fuels with various lubricity levels were included. Some additives and components, which may be used by the fuel users in the field, were also tested. The modified BOCLE test is a useful tool for classification of unadditized fuels and perhaps highly additized fuels. However, the method does not seem to be as useful, in its present form, for additive evaluation.