The reciprocating internal combustion engine has evolved over more than 100 years and now has very high levels of reliability, high specific output with low fuel consumption, and low emissions. Large marine diesel engines are capable of efficiencies of over 50%, but the effects of scale are such that the maximum efficiency will fall to about 45% for a large truck engine (about 300 kW) and to 40% for an automobile or light truck engine (about 80 kW). Reductions in efficiency with engine size occur because

1. The smaller the engine cylinder, the worse the volume to surface area ratio, so heat losses become more significant.