The piston assembly is the most complex tribological system within the internal combustion engine. In order to fully exploit its optimization potential a high level of system understanding is required. Therefore, in this paper experimental studies of two single cylinder engines are combined with CFD-simulation of the piston ring pack. The introduced measurement and simulation techniques enable a holistic approach to the investigation of the tribological conditions of the piston assembly. The results - like the comparison of crank-angle resolved oil film thickness to the piston assembly friction measurement - illustrate the implications of design parameters of the piston assembly on the functional parameters friction, oil consumption, blow-by, wear and acoustics and thereby permit purposive system optimization. (C) 2016 Elsevier Ltd. All rights reserved.