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During the past years, extensive research efforts have led to the development of diesel engines with significantly improved power concentration and fuel efficiency as compared to the past. But unfortunately, the increase of engine thermal efficiency is accompanied by a sharp increase of peak cylinder pressure. At the moment, peak pressures in the range of 230-240 bar have been reported. Naturally, a question remains as to whether such increased peak pressures could have an overall detrimental impact on mechanical efficiency. Initially, it was expected that these would have a negative impact and this was the motive for conducting the present work and developing a detailed friction model. Up to now, various correlations have been proposed that provide the friction mean effective pressure as a function of engine speed and load mainly, neglecting the effect of peak pressure or using data up to 130-140 bar.