We lived at 8500' elev. when I bought the this truck w/6.0 Diesel. It produces a lot of power at hi elevation. Easily hauls a 3 ton Bobcat on utility trailer up hill. The injectors are sensitive to dirty oil and fuel. Had to replace injectors after ruining them with biodiesel extended oil changes. Upgraded to Elite Diesel Stage 1 inj and new flash. Now change oil every 3000 mi or less, use Seafoam fuel treatment, and engine is much happier. Burnt up one alternator at 84,000 miles. Replaced it myself in 10 minutes for $200. No other repair problems. Mileage around town is 16-17 mpg. Highway is 22-26 and truck is comfortable on long trips.
Any web search of the infamous Ford Diesel will let you know, its not if but when you will be spending a lot of bucks to rebuild the engine. Removal of the entire cab is necessary to gain entry to the engine. A defective EGR, Oil Cooler or over boosting Turbo Charger are all blamed for the head bolts stretching, and allowing the heads to left when the compression gets too great. The fix is spending $3,000 to $8,000 for new head gaskets, checking or replacing the heads, $1,000 to rebuild the Turbo. Replace the oil cooler and EGR, just in case. The 2008-2010 get terrible gas mileage and the 2011 needs a urea tank filled every 3,000 miles
Good truck overall. The brakes are exellent, interior is spacious and well thought of. My only main complaint would be the fuel effiency. Driving carefully in the city I dont get much more than 10 mpg. I would by this truck again if I had to.