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In a previous paper (SAE 951035) Daimler-Benz and Shell advocated that fixed oil drain intervals should not exceed 15,000 km or annually. This paper describes further experience, with data from various field trials and engines, allowing engine condition to be considered in relation to lubricant ageing and condition. Based on this Mercedes-Benz have introduced ASSYST, a new passenger car maintenance system which processes customer-specific operating data and calculates oil change intervals. Unnecessary oil changes are avoided, conserving resources, and changes are not overlooked assuring durability. Intervals between 15,000 and 30,000 km are enabled, corresponding to between 1 and 2 years, representing a time extension of about 50%. Premium quality oil permits a longer interval, thus the customer sees an immediate benefit. This study shows that lubricant continues as an important engine design element and illustrates the environmental commitment shared by both companies.

Secondary air injection after cold start gives two effects for reduced exhaust emissions: An exothermic reaction at the hot exhaust valves occurs, which increases the temperature of the exhaust gas. It gives sufficient air to the catalyst during the cold start fuel enrichment that is necessary to prevent driveability problems. Handicaps for the wide use of air injection include space constraints, weight and price. An electrical air blower was choosen to best satisfy all these requirements. The development steps are described. The result is a three stage radialblower with extremly high revolutions of about 18000 rpm. The system configuration and the outcome are demonstrated on the new C-Class of Mercedes-Benz. The results show emission reductions higher than 50 %, while also satisfying the development goals of noise, volume, weight and cost requirements.

Lubrication of moving parts becomes less efficient in those areas where close fit limits the amount of lubricant to a very thin oil film. Journal bearings are particularly vulnerable in this respect. To test the degree of wear, a radioisotope technique was applied in which shafts and bearings were deuteron activated. Not only did the tests prove sufficiently sensitive to determine the full range of hydrodynamic lubrication, but they also identified the transition point at which poor lubrication caused journal-bearing wear. It was also found that materials of the shaft and bearings greatly influenced the amount of wear.