Last week I was towing at max load (6300lbs, tall enclosed trailer).
My mileage was down (12 instead of the usual 13), and more importantly I couldn’t get it up over about 82mph going up some long hills. It was about a 160 mile tow. Normally I have no problems cruising at 85 up and down these hills. Ambient Temp was 91F.

After I arrive and unhitched, the X5 ran great. Plenty of power and i noticed much better than normal mileage (28 rather than 26mpg) around our rural town.

Do you think the hot weather is the main reason I was down on power?