2021 Ram 3500 H.O.

I will also point out that in general emissions that are bad for the environment like CO2, HC, and CO decrease dramatically with higher compression ratios. However, due to the US EPA's hard on for NOx ,which is only harmful to people in very heavily populated areas and is not an issue for those who don't live in areas with a population of 2 million people. US diesel owners have to suffer in added complexity, lower fuel economy, worse environmental emissions, less reliability and so on to keep NOx low so people can live in metro areas with very large populations just in case we might drive in there.