I don't believe those claims either. And, I think MPG like that might only be possilbe when you have very steady and consistent RPMs, and that is not how gas engines run...
I've gone in the opposite direction of some of you posting here-- I got rid of my gas f150 (was pretty dead beat anyway) and i got a '98 RAM2500 with 6 cyl cummins diesel. I tow lite things like wood splitters, tractors, etc. and, very occassionally. I do haul wood and stone, but again, occassionally. I bought the diesel because of the opportunity to run it on alternative fuel sources (e.g. biodiesel and grease). The week after next I'm trying biodiesel for the first time... And, I'm actively looking into grease burning conversion kit... Right now, with my current configuration, I'm getting 20-23MPG on my truck.
Diesel costs so much because there is such a HUGE demand for gas. Both from the US and more importantly asian world countries... (which are using fuel at an alarming rate - china and india) The crude sources are being competed for to produce more GAS.
Yesterday Crude reached an all time high- 66.00 per barrel. And, the surplus supply of gas continued to dwindle for the strait 6th week... People won't be able to afford to heat their homes this winter... And, my opinion is that within 5 years, ppl won't be able to afford to drive nearly as much as they do today.
Here are some sites which have interesting and scary reading...
www.dieoff.org
www.oilcrash.com
I strongly suspect that in 5 years or so, power blackouts, food shortages, and lack of transportation availability, will be common issues
There is no strong replacement for fossil fuels. Basically, we're screwed...