Sweet speed: ford ranger?

[greenitup]

i drive a ranger and it has 5 gears and everything is stock
you can pop into 4th on a flat at 30 mph, and OD in 45 (these are for flats)
so i travel around 40 mph in 4th and 55 in OD (this allows easy climbing of small bumps)
do you think that it is more efficient for me to travel in 4th or OD
I have been thinking 4th may be more efficient because of the slower speed but the OD is a higher gear, I also don't have a scangage so i am trying a few tanks at 4th but there are alot of variables (i carry stuff in the back of the truck)
i get around 29-30 mpg and am hoping to bump it up more.

[SVOboy]

It's hard to say, but usually higher gear at any given speed = better FE. I would buy or borrow a SG to test it out.