heavy vehicle engines have more pollution gear then the current passenger vehicles. and yes they too have there issues with everything. but instead of it happening at 50,000kms its happening at 300,000kms. for example. because most heavy vehicles are doing big kilometers. ours are doing 200,000kms to 250,000kms per year. so when we trade them in, usually every 4 years, they are getting very close to the million. if your happened to drive a newer diesel car those sort of kms. (not that i can see anyone driving a car that far.) they would most likely do the same sort of kilometers. problem is they dont get hot enough(not working through every gear) which is what diesels love. and they don't stay hot enough for very long. to allow all the emission gear to do its job properly. (short trips to the shop spent mostly at idle)