I drive a '01 Dodge 2500 ***mins HO w/ 6 speed tranny. Pulling an overloaded cargo trailer, 6x7x10 (much like a big parachute) I am getting 15.3 mpg consistant. When running empty 21.5-22 mpg. I am adding a Stonewell as soon as it gets built and hopeing for around 18.5 - 20mpg we'll see. The truck currently has 112,000 and climbing, but running better now than when new. As far as cost effective with my yearly milage and the price differences I figured around 2.5 years to break even! However with a life expectancy of 3 - 500,000 miles (how long can you stand to drive the same vehicle) years won't be an issue. Living in East TN the diesel out performs the gas 4 fold pullng hills. As far as maintenance I change the oil and filter every 5,000 book says 7,500. Fuel filter about avery 15,000. Oil 11 qts and filter about $30 or less. Fuel filter $25 or less at Autozone. However no plugs or plug wires. Anyone truly interested in the cost difference needs to see Robert Withworth, CF at the Convention, he has a good program on cost analysis Gas Vs. Diesel. When all is said and done I'll never buy another gas for a primary vehicle.