I asked Mapquest and Google Maps directions from Washington, DC to State College, PA. Google Maps says: 216 mi (about 4 hours 38 mins). Mapquest says: Total Est. Time: 3 hours, 49 minutes Total Est. Distance: 208.20 miles.
I won't quibble about the difference between estimated distance, but the difference in estimated time is greater than 20%. Why is that? Looks like basically the same route to me.
Maybe Mapquest users drive faster.