HDI engines have been around for a long, long time
but todays HDI engines are a totally different beast to those of even just 10 years ago. The principal is the same, you compress the fuel air mixture enough to heat it up to it's flash point and it goes boom but the mixtures are different, there is recirculation and then there are the external components to clean out what the current 'self proclaimed' world government deems undesirable out of the exhaust gasses.
Just as soon as the engine manufacturers have redesigned & tweaked the engines to meet the latest standards they'll find something else to impose on the industry. As for all those preaching the coming saviour of the car industry in the all electric vehicle, well - the electricity needs to be generated and very few places provide free charging points.
But back to the original point. I suspect that asking about the emissions on a used car is likely to be low down on the priority list for buyers. The top of the list will be more likely what's the price, how much are you willing to drop that price, service history, fuel economy and insurance costs. Following those will be..... how many miles has it done, if a high miler has the timing belt has been replaced, has it been involved in any accidents, is it HPI clear, what extras it has (read what toys does it have) then maybe what's the emissions
