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I have a 2000 F-250 with the 6-speed manual transmission. In city driving I get just over 19mpg (this is with continuous stop-and-go and playing around with the turbo somewhat). In highway driving (~70-75mph) I only manage to get 16mpg.

I have 3.73 gears and stock size tires (265/75R16) and at 75mph my engine is turning 2200rpm. I imagine the reason for my poorer highway economy has to be due to this higher sustained RPM and therefore due to the 3.73 gears.

I do use the truck for some towing, however, the largest load it will ever see for the forseeable future is a 4000lb 20' boat. I imagine I would still have plenty of pulling power available for such a light load if I regear.

Does anyone have any recommendations as far as new gear ratio in consideration of pulling the boat, maintaining good fuel economy in the city (should only improve/maintain with higher gears), and improving it on the highway.

Thanks.