[hatzie]

Red block 6.2 diesel. Completely gutless. But... 25mpg is doable on the highway with that engine. You need to keep close track of the RPMs and not lug it or over-rev...
I've gotten just over 22mpg with my 6.5L twice. My overall average is 19. My Mileage widget tells me I used 3394 gallons of fuel over the last 10 years and 65,440 miles.