My old gas engine truck went in for oil change at 3-4 k. My diesel goes in at 6-8k. I get 20-21 miles mixed city/hiway empty and 13-15 pulling loaded trailers. I haven't pulled my 5th wheel enough to get a decent reading on mileage but I have pulled thousands of miles with loaded flatbeds, tractors and cargo trailers up to 10k. The diesel has 177,000 on it and it has never had an engine or drive train repair. It is 9 years old this year and still looks nearly new in and out. When I go to a car show and hear some one say "They don't build them like they used to" I say "hallelujah". My point is, The newer diesels get very good mileage and have a longer service interval and the extra years they will serve more than makes up for the higher price not to mention the much higher resale value. In the long run the diesel is by far the cheaper ride. IMHO