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Diesel fuel lubricity has continued to be a topic of interest for the suppliers of diesel engines, diesel fuel injection equipment, diesel fuel and diesel fuel additives. The term “lubricity” has become commonly used to mean the ability of a diesel fuel to prevent or minimize wear in diesel fuel injection equipment systems that rely on the fuel to provide lubrication. Distributor and rotary type injection pumps are examples of systems that rely totally on the fuel for lubrication. These systems are commonly used in light and medium duty diesel engines. Shell Canada has been investigating the lubricity performance of diesel fuels for a number of years. We have continued to evaluate the lubricity performance of various diesel test fuels and additives in a specifically designed distributor type pump rig that has been described previously (1, 2, 3).

This paper describes a test program where up to eighteen diesel fuels of varying qualities were tested for cold performance in sixteen commercial diesel engines. In this study, cold performance was defined as the time to start, intensity and time of white smoke emissions after the cold start and engine knock, if present, after the cold start. Initial tests were run at -20°C with starting aids (such as block heat and/or ether use) and at -5°C with no starting aids. Subsequent tests were only run under the latter conditions, as this was found to be more discriminating regarding fuel quality effects. The diesel engines were chosen to represent the diversity of engine design in North America, Europe and the Far East. Both Direct and In-Direct Injection engines were tested as were naturally aspirated and turbocharged engines. Engine build dates varied from 1980 to 1989. This range covers most of the current diesel powered fleet in North America.

The tailpipe emissions of seven 1991-92 model years vehicles were measured at two different ambient temperatures (-7, 25°C) with three different base fuels. As expected, the emissions of the first bag were most dominant over the whole FTP cycle at the lower temperature. For the whole fleet, the HC, CO and NOx, emissions at -7°C were 3.8, 4.9 and 1.2 times respectively higher compared with the emissions at 25°C, while for the first bag of the FTP cycle, they were 5.1, 6.9 and 1.3 times higher. The increase in emissions at low temperature was found to be mainly vehicle dependent. Tests performed at 25°C showed good agreement with the Auto/Oil AQlRP results regarding the HC and CO emissions but showed some difference with respect to the NOx, emissions. However, the vehicle responses to the fuels were significantly different between the two temperatures.

A total of 54 Canadian Diesel Fuels were sampled in the winter of 1994/95. Both Regular and Low Sulfur (less than 500 ppm by mass sulfur) fuels were sampled. All the fuels were obtained directly from refineries and were intended for commercial sale. The fuel samples were evaluated for lubricity, as measured by the High Frequency Reciprocating Rig (HFRR) at 25 °C, and by the Scuffing load BOCLE (SLBOCLE) as developed by the Southwest Research Institute. Various relevant inspection properties were also determined. Total aromatic content and aromatic type (mono, di or poly) of the samples was also determined by High Pressure Liquid Chromatography (HPLC). The lubricity evaluations obtained are discussed, and compared to the other parameters obtained.

In the last few years there have been sporadic complaints regarding field failures of diesel fuel injection equipment. Upon investigation these complaints have been associated with: i) rotary or distributor type pumps as used in light and medium duty diesel engines, and ii) the use of “winter” grade diesel fuels or diesel fuels that have been altered to meet the requirements of environmental regulations. Rotary and distributor type diesel fuel pumps rely totally on the fuel for lubrication. The fuel's ability to prevent or minimize wear in these types of pumps is important. This ability has recently been referred to as the fuel's “lubricity”. Shell Canada has been investigating this issue for the past few years. Recently we have investigated the “lubricity” performance of various diesel fuels using two diesel fuel pump endurance rigs. One rig consists of two rotary type pumps, the other two distributor type pumps.

Three joint Government/Industry program have been reviewed to evaluate the effect of fuel properties and source on exhaust emissions from three post 1994 model year heavy-duty diesel engines, a single cylinder research engine and a prototype multicylinder engine designed to meet the 2004 model year oxides of nitrogen limit. The three post 1994 engines tested (at Environment Canada's facility) were a Detroit Diesel Series 50, a Caterpillar 3406E and a Cummins N14. Exhaust emissions of NOx, PM, CO, HC, and CO2 were measured using the “hot” US EPA Heavy-duty Transient Test Procedure. The single cylinder Ricardo Proteus research engine (run at the National Research Council of Canada) and the multicylinder Caterpillar 3176 prototype engine (run at the Southwest Research Institute) were tested using the AVL 8 mode test cycle. Fifteen fuels were tested in total: three “reference” Commercial Low Sulphur diesel fuels and twelve experimental fuels.