6.5TD MPG Hiway mileage Poll!

[Captain Jojo]

Hello,

Am getting 16 mpg at 63mph empty, with a 6.5 TD and 3.73 gearing in the back, 4L80e transmission and cutaway van with box (1 1/2 feet above cabin).

Got a couple of questions since I want to trim it to get as best of mpg on the highway at 65 mph as possible. Will not tow and run this van almost empty (will convert it to a RV):

Does anybody have experience at what rpm the engine runs with the 3.03 gearing of the rear axle instead of the 3.42, and if it still drives ok (not too sluggish)? What is the thinnest tire with the same outside diameter on this rig? I heard somebody using (harder) military tires for less rolling resistance and am wondering if that would be an option to consider. Am working on getting a wind diverter, too. What else can I do (IP is in good order)?

Thanks a bunch up-front. Am new to this croud here and must say that the abundance of info is overwhelming.
J

[JohnC]

I had 3.42 gears in my '93 and would not recommend going any higher than that unless you're putting it in a Corvette or something else really light.