Federal regulations require all highway diesel fuel to have a maximum sulfur level of 500 ppm, effective October 1993. California regulations require a maximum 10% aromatics content in addition to the low sulfur content. The hydrotreating processes used to reduce fuel sulfur and aromatics contents to meet these new regulations have the potential of reducing fuel lubricity by reducing the amount of polar impurities such as nitrogen compounds which provide lubricity. This is a great concern for many fuel injection equipment suppliers and fuel producers.
Several low aromatics diesel fuels were produced in a pilot plant facility and analyzed using a Ball-on-Cylinder Lubricity Evaluator (BOCLE). These fuels were then tested in a pump endurance test facility using two types of fuel-lubricated rotary-distributor fuel injection pumps. Vehicle testing on a chassis dynamometer was also conducted to demonstrate the lubricity characteristics of a regular diesel fuel compared to a very low aromatics fuel, with and without a lubricity additive. This paper presents the results of these laboratory, pump stand, and vehicle tests, resulting from a cooperative study between Chevron Research and Technology Company and Stanadyne Automotive Corp.