The older models (pre-90's) go a total of 55mph and get about 10-15mpg HWY, but they pull 30 tons.
The newer models 90's up have a high/low overdrive and can go 65-70 mph @ (Depending on load) 13-15 mpg. I've heard that they can get better HWY but have not seen it. They are all time 4X4, but when you get into mountain terrain the gas mileage can drop to as low as 4 mpg.
I had a uni 404 for a year that I picked up for 12,000.00 in Alma, CO. It was an older model and was a beast. I do not recommend the older model unless you are a tinker and like life in the slow lane. I had four VW Buses and 6 land rovers so I like to work on my own trucks. It took constant maintance to keep it at tip-top shape. I sold it because I felt the camper was too small and the vech too slow for my tastes. The newer ones are much more hwy friendly.
Remember if your serious about a vech like this Volvo, MAN, Tarta, and many others, make a large backcountry vech. The Volvo's can drive as high 90 mph, they make 4X4 & 6X6's with whatever cab you want on it, but they are very pricey. I'll put it this way; they can make a hummer H1 Alpha look very cheap.
Bob, A friend of mine in Cody (WY), has his for sale for $36,000.00 [Oops, actually selling for $47,000]. (I don't Know if he has sold it yet[not sold yet]) and it is a 416 DOKA Expedition Unimog (pic below). I don’t know what kind of gas mileage that one gets or hwy speeds, because I never drove it. If you are above six feet tall, I'll warn you that the older mog's are not very accommodating. I’m five ten and fit into the driver seat perfectly, but I would not want be taller.
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