Comment Re:Compressed air. (Score 1) 204
Diesel hybrids aren't really practical due to the way they work. Diesel engines just aren't suited to being started and stopped constantly like that, and because of the high compression ratios needed for diesel to work, it wastes quite a lot more energy every time the hybrid system has to restart the engine (then there's the heat and lack of heat problem-- my Prius often has to waste a bit of fuel just to keep the combustion system warm enough to control emissions as it is). I think that's one of the big reasons Toyota decided to use their modified pseudo-Atkinson cycle engine instead for their hybrid systems-- they spent a ton of time and money researching and developing it, and it's the most popular system today because it's so well designed. The variable compression ratio makes them a lot more efficient than diesel would be in the long run too, although the efficiency is relatively close in most cases. But I suspect that the main reason is that of emissions. You can keep the emissions much lower with gas than with diesel if that's what you tune it for.
You're right about the (ancient) notions of diesel in the U.S. though. I've seen a lot of modern Mercedes diesels here in the U.S., and unless you know what the Blu-tech badge means, I think most Americans wouldn't have any idea they weren't running on ordinary gasoline. The technology has come a long way since the old days, although since American trucks are about the only diesels most people here see, they probably believe the smoke-belching, noisy behemoths are the only way diesel can run even today.