Maybe we just have too much tax on petroleum in my area. I passed a station this morning with Reg $3.599, Diesel $3.479 and have often seen the price of Diesel less than regular here in Chicagoland.
Most vehicles that I've researched petroleum vs diesel, the diesels have a greater percentage of additional mileage than percentage of additional fuel cost. The only downside I've seen to purchasing a diesel is the additional cost of the engine, but they are usually known for their longevity and higher resale. Diesels also have the benefit of being able to burn homemade bio-diesel or be fitted with a heated veggie oil fuel system. My brother is in the process of converting an international chassis bus into an RV and will have a couple big veggie oil tanks under it with onboard filtration. We've read where people have gone coast to coast having only filled their diesel tank once, filling up their veggie tanks (with permission) at various restaurants.
I'm a bit of an fuel economy geek. GasBuddy and Fuelly are heavily used by me. I do what I consider a light version of hypermiling, my van Green is averaging just over 20 mpg intra-urban driving, it's rated at 14c/18h/16c. I'd love to put a small turbo-diesel in it, fairly certain that I'd be able to get over 25 mpg, possibly as high as 30 highway.
