I routinly tow an TheMightyHobie18 with a VW Passt 1.8T (manual) at 75-80 mph. When in a hurry I have been known to go as fast as 90 mph. This is with a new trailer that tracks well, is loaded properly, has properly inflated tires rated for high speed, and there is not a strong crosswind. I also usually have a bike or two and a kayak or two on the roof rack as well.

I would not do this with any tow vehicle or trailer. Both are in excellent condition.