I have found on my two 800XC that my best cruising mileage is between 25-30 mph.
If Im taking it easy both of them will hit in the low twenties and if im playing and running fast I get around 18 mpg.
Ive averaged as high as 24mpg on the 22 and 22mpg on the 23
Borth of them will exceed 70mp, but they just purr along at 20 to 30 mph.
the 22 has the msc air inlet (the only thing worth a tin plated turd they have) and an RJWC pipe with stock exhaust and has 27" Sniper 920s on it.
the 23 I installed an RNG primary clutch kit to eliminate the lag (and will be installing one on the 22) and its still on the CST Abuzz 26" tires.
It isn't a slam and jam kit, just a slightly softer spring and 18gram weights instead of the stock 16gram to kick the variator into action with less energy expended.
that primary kit did more for throttle response and lag elimination than anything else. it also made the machine a lot more tractable on steeper descents.
Mind these are 800Xc, not the 1000 but its the same drivetrain, same block (different cylinders)and chassis and so forth.
But mostly, ya gotta find that "sweet spot" in the engine.