[factoryrat]

The EU standards are equal to or better than US standards. AND, their standards have been in effect longer than those in the US, like ULSD standards for example.

The EPA does NOT want diesel engines in US passenger cars, PERIOD!

This has been the unwritten mandate for as long as I can remember, and was the mandate since I left the auto industry a decade ago.

US passenger vehicles get far worse mileage than they did 25 years ago, and it is all due to EPA “emissions” requirements.

The dirty little secret is that current US vehicles are worse polluters now than cars built at the end of the 20th century.

[RayChuang88]

The big issue with diesel engines is the complication of cleaning up the elevated NOx gas output and particulates from diesel exhaust, both of which are seriously harmful to human lungs (that's why for many years people living near railroad yards had elevated levels of lung ailments due to the steam engine, then diesel engine exhaust emissions).

Modern diesel engines used on diesel-electric locomotives and oceangoing ships have very sophisticated systems to remove the diesel particulates and reduce the NOx output using various forms of selective catalytic reduction (SCR). You see them on BMW and Mercedes-Benz turbodiesel automobiles, and they are very expensive to implement (it costs about US$2,500 to US$5,000 per car). At those prices, it'll be actually be cheaper to build a true gas-electric hybrid, as Toyota has shown with the standard Prius (circa US$22,000 to US$32,000 depending on options).

I do know that VW and Mercedes-Benz have sold gas-electric hybrids in the US market. It's likely that both companies may push for more gas-electric hybrids sold in the US market until HCCI engine technology is ready a few years from now.