The Influence of Lubricating Oil Age on Oil Quality and Emissions from IDI Passenger Car Diesels 1999-01-1135

Two Ford IDI passenger car diesel engines, 1.6 and 1.8 litres, were tested over a 100 hour lube oil ageing period with engine out emission samples every 15 hours. The 1.6 litre engine was tested with 5% EGR and the 1.8 litre engine with 15% EGR. Comparison was also made with previous work using an older Petter AA1 engine. The three engines had different dependencies of particulate emissions on the lube oil age. The 1.6 litre engine increased the particulates from 1 to 2.5 g/kg of fuel, whereas the 1.8 litre engine first decreased the particulate emissions from 3 to 1 g/kg over 50 hours of oil age and then they increased to 2 g/kg at 100 hours. This was similar to the previous work on the Petter AA1 engine, where the emissions first decreased and then increased as the oil aged. For the 1.8 litre engine the lube oil fraction of the VOF was high with fresh oil and decreased with time for the first 50 hours and then remained steady. Thus the lube oil VOF was mainly responsible for the particulate decrease in the first 50 hours. The increase in the particulate mass after 50 hours was due to an increased unburnt fuel and carbon fraction and this also occurred for the 1.6 litre engine. The carbon in oil was least for the 1.8 litre engine but carbon was accumulating in the oil at a higher fraction of the carbon emitted than for the other engine. This varied from 7 to 17% and this rate of carbon flow into the lube oil was higher than has been reported by others and may indicate that low emission diesel engines with EGR have a greater flow of carbon into the oil as a proportion of the carbon emitted.