yes but never the less they do produce NOx thankfully they don't follow the pattern of the other so called low NOx producer. the petrol engine which by 50,000 miles and all things being equal produces as much as the diesel engine then goes on to produce more so. shame all testing seems to be based on new engines and not on lifetimes.....ProfJohnL said:Not quite right, Steam engines don't produce much NOX :huh:Gabsgrandad said: