I wouldn't cruise there because;
A) that's a lot of wear and tear on the engine About 70% more.
B) NVH. Noise,Vibration and Harshness.
4000 at 65 is friggen loud. And
C) the driveshaft is whipping around something fierce.
D) the rear end is running a lot warmer, and is gonna want a better oil.
E) the automatic is gonna run warmer too..... and it puts it's heat right into the coldest part of the rad...... which then immediately goes into your engine. So your cooling system has to be up to the task.
F) RPM Sucks gas.
