It appears that earlier AWD Fusions had issues with their PTU units, as did other Ford vehicles because it's supposedly a "lifetime gear oil" fill. It's not lifetime. I know Ford made improvements in the PTU design as far as leaking seals but they still claim it's still a "lifetime" fluid, but it's not, especially with the exhaust heat of the 3.5 EB engine. Though I'm not sure the Fusion could be had with the 3.5 EB, though exhaust heat in general is a problem if the exhaust is run close to the PTU. Changing the fluid every 20-30,000 miles from new seemed to help keep the fluid a viable fluid and not turn it into sludge. Not sure whether Ford included a drain plug for the PTU in later models in the Fusion. Otherwise you have to suck out the old fluid through the fill plug.
Whimsey