Well, I don't know exactly what they did but I do know that they tryed to build a diesel engine for passenger cars some 20 years ago. In the mid 90s they still weren't done so Opel/Vauxhall, a GM company had to buy diesel engines from BMW (not the best choice either...) to put in their cars.

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'99 S420, 155k
'91 VW Vanagon GL, 150k
'85 VW Vanagon GL, 120k
'82 VW Westy, aircooled, 165k