lecause the diesel is inherently more ifficient than a gasoline
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engine a sr proportion of the heat of combus s wasted and in total less heat has conducted away from the combustion )er to the cooling water and via the st for a given specific output. Whether or not this favours the diesel with regard to piston and valve life is, however, problematical. For example, an exhaust valve that can cope with a large amount of heat might fail prematurely because of high transient temperatures. And in another case it might be more liable to failure because the overall heat flaw was too great at sustained high loads. The heavier piston of a diesel can absorb more heat than the lighter piston of a gasoline engine because it can act as a heat sink, and the amount of heat to be dissipated over a complete cycle may be more important than the peak temperature given that it has good heat-flow characteristics. The factors involved are, therefore, complex and it is impossible to give an unqualified answer to your question.
In a reported case of a well-known type of diesel being converted to operate as a gasoline engine, however, the exhaust valves and pistons of the converted engine -gave trouble" after a relatively short period. The converted unit produced the same output at the same speed as the diesel, which has a favourable reputation for long life in its basic form. In the opinion of the specialist who made the conversion, a robustly constructed gasoline engine would be less reliable than a diesel if it operated continuously at a high load, because of heat dissipation difficulties. And it is also noted by the specialist in question that diesel fuel is "kinder to exhaust valves" than gasoline fuel.