I've got a 87' w150 with a new jasper motor in it. It has approx 12,000 miles on it with cams, lifters, headers, the works. As it is it only gets about 10mpg. I've recently thought about puting a totally rebuilt stock 5.2 318 crate in it with less than 1000 miles on it to improve gas mileage. One friend of mine told me you can't beat the jasper and it'd be stupid to swap it out. He said just take the cams and lifters out and it should get at least 15-16mpg. I'd like to find a happy medium between power and efficency. Any thoughts or suggestions would be greatly appreciated!

 

I've only ever heard of one guy who got over 14mpg in an old v8 4x4, and that's a guy on here. Everyone I've ever known has been in the 8-12mpg range. IIRC the Jasper crate motors are relatively mild builds and I don't think you'd see all that much of an improvement. I actually got better mileage after putting a cam, headers, intake, carb, etc. on my w250. Of course I lifted it and put bigger tires on it so I'm back where I started from mileage wise, but it's still a lot faster now.