... at 60 mph, 78 kW!

If a car gets 30 miles per gallon, and travels at 60 miles per hour, it burns two gallons of gasoline per hour.  To figure out how much power is involved, simply divide the heat content of gasoline (2 gallons times  140 million  joules per gallon) by the time (1 hour = 3600 seconds).  

The result is: 78,000 watts.