You're thinking about that wrong. The Contour fans can move about 3,500 cfm on low speed and 5,000 cfm on the high speed. What I'm saying is that the volume of incoming air when the car is moving is more at speed is more than 3,500 cfm. It's more than 5,000 cfm. So there's no point to run the fans at that point, the incoming air alone will do a better job than even running the fans on high. Having the fan spinning disrupts the air more than having them off. And even if that wasn't true, running the fans when the incoming air exceeds their capacity on even their highest setting is just a waste of energy.
It shouldn't. At freeway speeds my car cools down to the thermostat temperature even when it's 100°F outside. The fans themselves are not a significant obstruction at speed, they're designed not to be running when the car is moving at speed. Less than 35 mph or so sure, the fans will need to run because the airflow through the front of the car isn't enough. But faster than that you shouldn't need them at all if everything else in your cooling system is working properly. That's how those fans work on a Ford Contour, and those things have very little grille area (which is why they needed such a good fan).
I don't like the thermostatic switches. Seems like a lot of problems come out them. I haven't had any issues with my Dakota Digital fan controller, and I can program my fans to start and stop at almost any temperature I like.
If you wouldn't know then why comment?
Funny that the auto industry as a whole did exactly the opposite and moved on from the mechanical fans.
If you run electric fans capable of moving the CFM needed for your car, and control them well, then electric fans will be more efficient than a mechanical fan. That's the big reason that the vast majority of cars use electrics now. People have issues with aftermarket conversions to electric fans because they either don't buy fans that are capable of moving enough CFM, they don't wire them correctly or provide for enough power, or they don't control them properly.
