Sounds like it was the starting point of developing cleaner running diesels. I have learned about some of this through my 2003 6.0 powerstroke on how it operates.
EPA regulations have pretty much made diesels in small sedans unfeasible. In Europe it is common for small sedans to get 65-70 mpg. The few offered here now are in the 40+ mpg range. So it is environmentally friendly to burn almost twice as much fuel with a more expensive and costlier motor to maintain?
When you have bureaucrats with no background in engineering, physics and thermodynamics making policy decisions, it's not surprising we are in the state we are. Then throw in lobbyists and political contributions and you have the perfect storm for bad decisions.
Many small diesel sedans can top the 50 MPG mark, including the Passat TDI with the manual transmission. Even the new E250 Bluetec Mercedes can get into the mid-40's on the highway. The reason the mileage is not better on US spec. vehicles is that they are seriously over weight and over-contented.
There's an awful lot of truth in your last sentence.
Based on my observations:
1) The cost (upfront and maintenance) of the emission systems are also driving the used tractor market. Most of my experience lies with ag tractors. As a very good example. My father has a 6415 (05' IIRC), it has about 850 hours on it. He bought it with 240 hours and the last couple of times he has been in the dealership they have offered to pay him more than what he bought it for.
2) These emission regulations require a complete new set of knowledge and certainly goes against convention when operating a diesel engine. Another example is my 6.7 Powerstroke. Previously I had a 7.3L Powerstroke, which is by far and away one of the best pickup diesel engines every, it sits right there with the 5.9L Cummins. You could let the 7.3L idle for hours to cool or heat the truck, it consumed ~.75 gallons an hour sitting. The new 6.7 HATES to idle, if you let the 6.7L idle for expended periods of time more soot will be trapped in the DPF and the active regeneration cycle will come on more often. During active regeneration diesel is injected during the exhaust stroke in the 7 and 8 pistons which then goes to the DPF where it is burned yielding ash, rather than carbon. Obviously extra diesel fuel will lower your MPG, by rough calculations every regen cycle costs me .5-.7 MPG per tank of diesel fuel.
Now I will also say that some of the doom and gloom predicted has certainly not panned out. One thing I heard is I would need to buy DEF every 5000 miles and it would cost 40+ bucks.... well 18000 miles later I am averaging ~$20 every 7500 miles. So not that bad...
Of course there are people that rip all the emissions stuff off new equipment... but that can be followed by a rather large fine.......
The regulations are here so we all might as well work within the system. It's like the incandescent light bulb... who knew we would miss those... waiting 5-10 mins in a cold garage for your lights to warm up is something I don’t really like....
I'm not happy to say I'm old enough to say I won't be owning an emission tractor. I like the old tractors anyway.
From Rudolph Diesel, inventor of the diesel engine; stated in 1912:
The diesel engine can be fed with vegetable oils and would help considerably in the development of agriculture of the countries which use it.
The use of vegetable oils for engine fuels may seem insignificant today. But such oils may become in course of time as important as petroleum and the coal tar products of the present time.