You can't just have the US, (especially the US) switch over to diesel to ease fuel prices. Think of it this way, market forces would kick in. With demand for Petrol down, Diesel goes up, and if your entire population of 300 million (half of them being large do nothing SUVS and trucks) started using diesel, the demand would increase SUBSTANTIALLY, and from there you're stuck with $3 or $4 per gallon of diesel. Not only does that happen in the long run, but also diesel emmissions are HORRIBLE. If you're ever stuck in Highway traffic around some trucks, you know what I mean. They're noisy, they're dirty, and they create SO MUCH CONGESTION around you. You speed up global warming that way, and the air gets dirtier. If you want my honest opinion, the world should get together to develop a Lithium Ion / Hydrogen / Synthetic Ethanol car. It's viable to produce ethanol from corn if for example you recreate the conditions and that could be done anywhere (Alaska, Antartica, the middle of the ocean on a boat, etc.) Have a completely new design of car that will have for example integrated solar panels on the body, wind generators or something extra to help charge a large battery, combine that with some sort of intense chemical reacting engine (uranium) and there's your super car that's cheap to run.
