The nature of analytical and experimental work published on combustion in internal combustion (IC) engines--including Diesel engines--is discussed. It is shown why the approaches used may not yield meaningful results. Avenues are indicated that may lead to more progress. Generally accepted models are contrasted with actual aerothermochemical processes in IC engines and it is shown that fuel jet mixing, gas motion, flame propagation, and turbulence are not modeled correctly. It is suggested that experimental techniques and analytical methods developed in the rocket combustion field may be useful if applied to IC engine combustion research.