I thought I would just give my 2cents on this.
Teh older diesel engines were very simplistic mechanical units made out of big ass steel components. Thus very reliable (not many things that can break) and would last a life time if maintained properly due to the super heavy duty engine and internal components. Unfortunately those heavy internals reduce the RPM range of the engine dramatically, thus while they can have great TQ with a turbo they still have a very narrow powerband, which irretated me beyond believe in the dunes in the Kalahari. All the diesels at the time (mid 90s) (turbo most of them) were struggling, while even the patehtic little gas engines would zing by on the soft sand dunes. Reason: the gas engines had a much wider powerband.
That has all changed with the latest and greatest marvels of diesel technology. COmmon high pressure computer controlled injectors allow much more precision and preiginition for the diesel. Thus they are a lot quiter and smoke a hell of a lot less. Add to that all the new emissions equipment and in the near future ( I believe next year) we will actually see diesels that can meet the new regulations in the US (specifically CA).
And yes we need those regulations. If we had a high % of diesels on the road similar to Europe the cities in the US would be unliveable from emissions, as folsk in the US drive their cars a hell of a lot more. Diesels require a hell of a lot of work to clean up the exhaust, not only particles, but the lean running engine and high compression create a lot of emissions problems they have very expensive and sophisticated solutions for now. Diesel has a only a few % more energy per volume than gas, the rest of the efficiency comes form direct injection, lean runnning and high compression, all of which creates a lot more emissions that need to be sorted out on the exhaust side. But I digress.
Added to the new injector control, they have variable vane turbos that allow low end torque while also allowign freer breathign at higher RPM (thus a wider power band). To go with all that new technology they also now make much lighter weight internal components (from aluminum as well) and also aluminum blocks and heads for diesels. That is great as the engine can actually go to high RPMs without destoying itself, adn doesn't weigh the front down like a boat anchor.
All goodness and great. Just a few catches. All this technology makes any modern gas engine look very simplistic. Thus expect it to be far more expensive than a similar gas engine. Added to that, this complexity will severely reduce reliability, especially compared to the good old diesel engines people think about. Longevity also takes a dive as it no longer uses "tank" parts inside either.
So don't simply add what was good of the old diesel engines with what is good of the new ones, as the only similarity between the 2 is that they use diesel. The new ones give all these benefits at a far greater cost, reduction in simplicity and thus reliability, as well as a reduction in longevity due the lightweight components used.
You can't have your cake and eat it.
Oh BTW the current hybrid technology is best suited to small light vehicles. Till the battery technology can catch up with the power requirements of large heavy vehciles, big hybrid vehicle benefits is pretty questionable.
Anyhow my 2c
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