It is hard to find vehicles with taller trannys. With my camry, it is not as tall as i would like, but will give about 45 MPG at 50-55 MPH. If you go faster it drops off quick.
I just bought a full size truck, because I am starting a homestead/farm. I looked around and thought about a diesel, but decided i couldnt afford one, since everybody is after them now. I have noticed though that the older diesel full size trucks are not geared nearly tall enough for good economy. Sure its nice to have a nice low first gear, but a nice tall fifth is just as important. If you are hauling a heavy load you can just leave it in 4th.
So I ended up buying a chevy 1500 W/T. They can be picked up for nearly nothing...I got one in good running condition, with many new parts for 750$...it just needed a passenger mirror and a windshield. I spent a while looking for one with the 4.3 L V6 and the 5 speed (the most efficient and a little unusual). i had to drive a couple hundred miles to get it, but am glad I did. On the way home I was going about 60-62MPH in the rain. On the tank I got 23.3 MPG...which is impressive for a full size. The 5 speed on this truck has very tall gearing, especially fifth. Going 60 makes it just barely possible to make it up hills without downshifting...though the engine makes plenty of power...you just have to downshift to find it. You can do 50 in 5th on a completely flat road...but the engine is barely spinning, and you will have to downshift to go uphill at all. I dont have a tach but am guessing under 1800 at 55 in 5th.
Just wanted to say I would highly recommend these trucks for hypermiling...I think I will be above 25 MPG once the weather is warm. They can also haul a large load and a fairly hefty trailer. I have not tried the engine off coast yet...it is a little bit more difficult with the cheap GM ignition and the large transmission/heavy clutch...but i think it should be possible. It coasts well, and it is very easy to keep the Revs low with the torquey engine.
I have a 97 F150 4X4 with a 4.2L V6 and a 5 speed manual, which has gotten up to 27mpg last summer, and with just the addition of a grill block, gave me 23mpg this winter at 55mph average speed. I'm sure that with some underbody panelling, I could get it up to at least 30mpg this summer.
Basjoos-thats impressive MPG for a 4x4...mine's only 2wd. I have yet to fully inflate the tires, and right now we are in mud season, so MPG sucks. I am hoping for 25-27 in the summer. I would love to put a grille block on it, but my temp guage sender needs replacement, so i will wait to do that first. The aerodynamics of the underneath (and the top) are terrible, but I noticed chevy put an airdam on the front of the truck presumably to funnel air to the sides and over the truck. I dont know if I will go all out like phil knox on the aero, but I will definately work on it.
Sludgy-I guess the best option is to drive it slowly on the hwy?