An Oldsmobile diesel -- the notorious 5.7-litre 350 cubic inch GM diesel engine gave diesels a bad name in the US.
Should the "dirty diesels" be scrapped once and for all in favour of cleaner technologies? There are those who think so, especially in the US -- but maybe they just haven't been paying attention. There's no such confusion in Europe, for instance.

Diesel engines power 37% of all new cars sold in Europe (62% in France), with the share predicted to rise to 45% by 2005 -- but fewer than 1% of new American cars have diesel engines.

One reason is the poor quality of diesel fuel sold in the US. A 1998 report on fuel lubricity worldwide found that diesel fuel sold in the US and Canada is some of the poorest quality fuel in the world. Fully 50% of the US fuel was found to be below the standards recommended by equipment manufacturers.
http://www.biodiesel.org/pdf_files/Lubricity.PDF

Big Oil has dragged it's feet in cleaning up diesel fuel in the US. Europe started producing cleaner, low-sulfur diesel fuel in 1990; the US plans to follow in 2006. And the new generation of clean diesels either can't meet the US emissions standards on the dirty US fuel, or they can't even use it. But they run just fine on biodiesel, with very low emissions.

For a possible view of the future, we have to look to the past. The Elsbett engine -- the 3-cylinder SVO (Straight Vegetable Oil) diesel motor designed by the late Ludwig Elsbett, was a highly advanced true multifuel engine, and the forerunner of all DI diesels made today. Details:
http://www.elsbett.com/
gd/eteche.htm
More detail (in German):
http://www.elsbett.com/gd/etech.htm
News article about a Mercedes fitted with the amazing Elsbett engine (120kb graphic file).

Diesel motor development is very advancing rapidly, with tremendous improvements in efficiency, economy, performance and emissions -- but not, as yet, in the direction of true mutlifuel motors that can run on petroleum diesel fuel, biodiesel, SVO, or any combinatioin of the three without modification and under full manufacturer's warranty. This is what the fast-growing international biofuels community is pushing for.

Meanwhile, there are signs of change in increasing use of diesels in the US:

"Panel tells EPA no technical problems getting sulfur out of diesel fuel" -- Washington, Associated Press, October 30, 2002: There are no technical problems that should prevent refiners from producing nearly sulfur-free diesel by 2006 when new requirements for the cleaner fuel go into effect, an advisory panel told the Environmental Protection Agency. The report by an independent review panel, whose members included both oil industry representatives and environmental advocates, concluded "there are no technological impediments" to refineries reducing the amount of sulfur in diesel from the current 500 parts per million to 15 parts per million.
http://www.signonsandiego.com/news/science/
20021030-1438-cleandiesel.html

"Clean-Air Czar of California Shifts to Accept Diesel Engines -- In Controversial Turn-Around, Regulator Sees Diesel as Alternative in Global-Warming Fight" -- The Wall Street Journal, October 24, 2002: For years, Alan Lloyd has regarded diesel as a dirty word, synonymous with brown haze and cancer-causing black soot. It's a view he has shared with environmental activists across the U.S. But in a striking change of heart that could alter the kinds of cars and trucks Americans drive, the chairman of the powerful California Air Resources Board is taking a new look at diesel vehicles. He thinks they're poised to emerge as part of the solution to a different environmental problem that's gaining more attention in the U.S.: global warming... Here, diesel engines are the greener option because they don't pump out as much so-called greenhouse gas as gasoline engines do... Dr. Lloyd says he has concluded that a new generation of high-tech diesels developed for Europe bear little resemblance to the smoke-spewers that Americans remember from the 1970s and 1980s.

 

I don't think they will ever be scrapped. What would happen to bus and train transit? Then you also have to throw in tractor trailers, dozers, loader and a crap load of other big equipment. Regular gas power will not be able to cut it.