I have also heard that diesels are the way to go. The only bad thing about them is it costs you an arm, a leg, and your firstborn child if it ever has to go to the mechanic LOL.
oh boy, this can of worms... there are so many people with SO many opinions there. me, i'm sold on old #2. had my powerstroke for almost five years now, and i love it. i wouldn't trade it, plus right now i COULDN'T.
the opinions start coming, AVOIDING brand wars as best i can... i'll talk from more of a ford point because that's what i KNOW, but GM and dodge are in the same boat, for the most part...
the older ones (95 to 03 7.3L powerstrokes) were generally pretty darn reliable. sluggish, but they'd do the job. late 03 brought us the 6.0 'strokers, which i have an 04.
so many out there mash and bash them because they're "junk." bull, there were some bad ones in 03 and 04 but with the sheer number of them that ford sold, they're really pretty few and far between. i've had some problems, but they're all due to those two years, and some of it is MY fault. higher mileage 6.0s are actually what i'd buy instead of low mileage because the LOWER mileage is more likely to be a lemon (hence why it lacks miles, in many cases). by 05 most of the problems had been worked out.
the 6.0 brought us EGR (exhaust gas recirculation, ala emissions b.s.). they don't take excessive idling well, not enough heat is created to burn everything out of the EGR valve at idle. but if you get a good one, they generally get BETTER mileage than 7.3s and WILL pull CIRCLES around a 7.3.
then we had the 6.4 from 08 to 10. it brought yet another emissions measure, DPF (diesel particulate filter). it traps unburnt stuff and when the DPF fills it goes into "regeneration." this is where it dumps fuel into the exhaust and burns off the crap in the DPF. many 6.4s get tremendous mileage, some didn't. 08's were the worst. like the 6.0's, it took a year to work out the bugs.
2011 brought us the all new ford built 6.7L powerstroke and another new emissions measure yet, urea injection. dunno real well how it works.
anyhow, GM with their duramax and dodge with the cummins have some similar issues/problems, but their timelines aren't totally the same. there's a LOT of new technology in the latest generations of diesels and the new emissions regs are hurting us BADLY. however, they're quite impressive machines. if ya want an oil burner, i'd look at an early 2000's variety, any brand. they ALL have their issues, but they're all supposed to be pretty good (and i don't like the duramax at all, but that's just personal preference on my part).
but for reference: i have an 04, crew cab, short bed, diesel 4x4, 6 spd manual. i average over 17 mpg, depending, i was averaging more like 19 with a K&N intake but took that POS off, bad for the turbo's health. anyhow, the people we worked for in NY had same year, pretty much same configuration with a 5.4l gas motor and an automatic and they averaged under 13. that's what i'll average on a LONG haul loaded. going local, and i drive less conservative loaded because i'm already burning heaps of fuel, it's more like 11.5 or 12. but it NEVER misses a beat.