The 800's get better than 6-10 mpg! They say it has a 25% increase in fuel economy over the 700 and I was getting 10-11 on my 700! My wifes 800 gets about 14.
Out west last year when we hit 110 miles the 1st sled to run out was the M1000, next was the 700. The 800's all made it back!
i'm talking about in the mountains not on the trail, if your getting 10 miles plus to the gallon all the time at 4-7k you must be a trail cruizer, i know on a deep day with us you'd be lucky to get 70 miles... on any M8!!!