Kollmann, K., Gürtler, T., Land, K., Warnecke, W. et al., "Extended Oil Drain Intervals - Conservation of Resources or Reduction of Engine Life (Part II)," SAE Technical Paper 981443, 1998, doi:10.4271/981443.
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.