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Effect of lubricant on particle emissions was studied using two heavy-duty diesel engines. Both particulate mass and particle number distribution were measured. Differences between lubricants were studied by dosing two percent of each lubricant (diesel engine oil) to diesel fuel. This arrangement was seen necessary to get clear differences between lubricants. The lubricant had a clear effect on particulate mass emissions. Two of the lubricants gave about the same emission as pure diesel fuel. The worst result was more than two times higher than without oil added to the fuel. The lubricants were all diesel engine oils with different base oils/additive package. Lubricant ash content presumably affects particulate mass. However, the difference in ash content between lubricants was no higher than 30%. Therefore, ash content can only partly explain the differences. The combustion characteristics and the sulphur content of the base oil are essential, too.

In a diesel engine, both physical and chemical properties of the fuel affect exhaust emissions. This study focused on the separation of some physical and chemical effects of the fuel on the NOx emission. The tests were conducted with a bus engine using four diesel fuels with different density and aromatics levels. The measurements were performed using five injection timing settings to screen the effects of changes in actual injection timing. When conventional diesel fuel was replaced by reformulated diesel, NOx was reduced 7-13 %. Changes in the injection timing due to differences in the physical properties accounted only for a minor part (10-25 % relative) of the total reduction of NOx, whereas the greater part of the reduction (75-90 % relative) was due to other reasons, mainly fuel chemical properties.

Diesel fuel was reformulated by reducing sulfur to < 0.005 wt-%, aromatics to < 20 vol-% and by limiting heavy polyaromatics. This reduced NOx, particulate, PAH and mutagenic emissions plus exhaust odor. Oxidation catalysts operated well. Less deposits formed in the EGR system. Fuel lubricity was enhanced by additives evaluated by injection pump tests and HFRR. Three years of field testing with 140 buses showed no fuel related problems. Oil change period could be lengthened and fuel consumption was unchanged. Demand for reformulated fuel was triggered by differentiating taxation based on quality. Fuels have been used since 1993 without problems. Life cycle analysis showed no increase of CO2.

Lubricity testing of reformulated diesel fuels (sulfur <0 005 w-%, aromatics <20 vol-%) was started in 1990. A 1000 hour in-house test rig with distributor pumps was used for testing fuels and additives. When lubricity is not adequate, excessive wear is seen in the pump. A field test on 140 buses each accumulating 150 000 - 250 000 km with reformulated diesel was carried out. Reformulated diesel has been on the market since 1993 without problems. Lubricity was evaluated with HFRR test and compared to the pump rig results. HFRR overestimated the need for lubricity additives. Fuel sulfur was found to be not the only indicator of lubricity and lubricity of low sulfur diesel was as good as high sulfur when other fuel parameters were kept constant.

Unregulated emissions of reformulated diesel fuels (sulfur < 50 ppm, aromatics < 20 vol-%) were compared to the European EN590 specification fuel (sulfur < 500 ppm, aromatics < 35 vol-%) in three IDI passenger cars and one DI van using FTP and/or ECE/EUDC emission test procedures. The effect of reformulated diesel fuels on the mutagenicity of particulate soluble organic fraction (SOF) was studied. Fuel reformulation reduced particulate emissions in IDI cars. Reformulating fuel by decreasing heavier aromatics - without decreasing final boiling point - reduced particulate mutagenicity on emission basis. At low ambient temperature (-7°C) particulate PAH and mutagenic emissions increased compared to the standard ambient temperature (+22°C) with all fuels.

This paper presents the results of a gasoline reformulation project carried out in Finland during 1991. The target was to evaluate MTBE and ETBE as gasoline components with respect to operability and exhaust emission performance. The oxygenated fuels contained 2 to 2.7 per cent oxygen by weight. The oxygenated fuels reduced exhaust emissions significantly at normal ambient temperature. For non-catalyst cars the reduction of CO was 15 to 30 % and the reduction of HC was approx. 5 %. For three way catalyst (TWC) cars the CO emission decrease varied from 0 to 10 % and HC approx. 10 %. The use of oxygenates reduced exhaust emissions also at low ambient temperature, but not as much as at normal temperature. Cold starting was quicker and cold driveability was better when oxygenated fuels were used.

Excellent fuel quality or fuel detergents are required to reduce intake valve deposits in gasoline engines. However, engine oils also have a considerable effect on the deposits. In engine tests the cleanest valves were found with synthetic multigrade or mineral single grade oils, both containing no VI improvers. Popular SAE 10W-40 and 5W-50 oils formed more deposits because they contain VI improvers. Deposit weight correlated directly with oil shear stability which is a measure of the VI improver quality. Both engine oil and gasoline have to be chosen correctly for a clean intake system.