My 08 Arctic Fox 5er came with ST 235 80R 16, Load Range E. From Pinehurst, Idaho (where we purchased the 5er) we took a trip to Washington, Oregon, Northern California, Nevada and finally home, which was about 1500 miles with the ST tires. The tires were inflated to 80 psi and we averaged 10 mpg. As soon as got the Arctic Fox 5er home, I had Discount Tire change all 5 tires to LT Michelin XPS Rib 235 85R Load Range E. The XPS Ribs are about 2" taller then the original ST China junk tires. On our last trip, with the XPS Rib, LT tires, we averaged 12 mpg. We held to the same speed, 60 to 65 mph, but we climbed far more high mountain passes. Is it possible for the Michelin XPS Rib to make that much difference in mileage?