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The introduction around the world of low sulphur diesel fuel has required extensive use of lubricity additive technology in some markets. At the same time, the use of performance diesel additives such as detergents and defoamers is becoming more widespread. The wider application of performance diesel additives demands the introduction of proven technologies in new markets, whilst new requirements are met with a combination of existing and new additive technologies. Such developments are not without risk. These new applications could generate a variety of field problems and extensive testing is necessary to prove that the use in a new environment is trouble-free. This paper illustrates how diesel fuel additives can be efficient in solving specific problems and, at the same time, can generate a host of new problems such as plugging of fuel filters, in-line diesel pump failures, increased level of engine bore polish and deactivation of other performance diesel additives.

The Co-ordinating European Council (CEC) for the development of performance tests for transportation fuels, lubricants and other fluids has set up a working group to develop a laboratory pump rig test able to discriminate between diesel fuels of different lubricity performance. This test was expected to correlate with the performance of fuels and Fuel Injection Equipment (FIE) in the field, therefore providing a way to avoid costly field trials. This test could also enhance the understanding of the results from the High Frequency Reciprocating Rig (HFRR) method. The CEC working group was supported by representatives of Oil Companies, Test Houses, Additive Companies and all the European FIE Manufacturers. After a thorough investigative phase, the group focused on a Bosch VE 4 distributor-type pump run according to the Bosch WP2 test cycle. This choice was also widely accepted throughout the industry.

A commercial grade of Bio-Hydrogenated Diesel (BHD) has been tested to assess its suitability for field applications. This BHD grade was partly isomerised and it was blended into diesel fuel at ratios from 5% to 30%. The testing done compared these blends to the fossil diesel and the fossil diesel containing 5% Fatty Acid Methyl Ester (FAME) from palm oil. The testing carried out includes a range of engine, field and laboratory testing to understand the impact of BHD on fuel specification, fuel performance, harms and diesel fuel additive requirement and appetite. An extensive program of laboratory testing has been undertaken to assess the impact of different BHD ratios on fuel specification and other performance and harms tests like lubricity, water interaction, anti-oxidant requirement and fuel stability at low T.

Fuel additives can contribute to maintaining the performance of diesel engines in a variety of ways. This holds true for current and future engine technology. Fouling of indirect injection engines (IDI) has been studied at length. Fouling of direct injection engines (Dl) is less known and less well understood. Problems associated with Dl fouling and a proposed mechanism for it are discussed. Additive effectiveness in preventing injector fouling is confirmed. Injector hole corrosion/erosion, as experienced in the Cummins N14 engine, can be avoided by the appropriate additive chemistry. Particulate traps can also benefit from ashless additive technology aimed at increasing the time between regeneration steps, hence improving effective trap life.

Additive technology has been used to enhance the quality of automotive diesel fuel in a number of important areas of performance. This paper focusses on the role of new additive technology in two important areas: 1. Maintenance of designed performance of injector systems: 2. Prevention of problems associated with fuels designed to respond to tighter emission regulations. Field and laboratory data have been generated in industry and in-house procedures. The implications of these results are discussed.