Seth,
Diesel gas typically costs less per gallon then gasoline. Long ago it cost a lot less...today it's about the same, sometimes higher, but usually about 10 - 15% lower. So it's cheaper to buy by the gallon.
The big plus is the mpg: diesel often gets nearly twice the miles per gallon...well almost, depends on the application. My company runs some large trucks, the gas models (with big V8's) got about 7-8 mpg, whereas our International intercooled turbo-diesels enjoy nearly 14 mpg!!! BUT these are large trucks with heavy weight. Diesel engines do great with producing lots of torque to pull heavy loads, so they are ideal for heavy vehicles.
The other benefit is longevity: the same International trucks have a rating such that 90% of the engines are expected to run 480,000 miles before needing an overhaul. The gasoline engine may only run about 200,000.
So there you BASICALLY have it; fuel economy & longevity. The downside is the higher costs to aquire, difficulty in finding the fuel readily available (not all stations have diesel) and when you do work on a diesel, it typically costs more then a gas engine.
The diesel has smooth low-end torque and that's nice for offroading slowly. It also sounds really powerful and some like the fragrance.
Course, when I smell diesel it always takes me back to the stern of a boat where a tuna, yellowtail or dorado are about to meet their demise...
