Let me preface this by saying that I got my FEH AWD a month ago and love it.

I was driving up Hwy 1 from Santa Cruz CA two days ago (no AC running at the time) and noticed that on some of the steeper hils the tach read 5K+ rpms. Given that the tach red-lines at 6.5K, is this something to be concerned about for long periods? I regularly see it in the 3.5-4K range on the highway, but this seemed a bit high.

 

Yeah, the high efficiency of the engine means that it will rev higher to accelerate uphill. 5K isn't that bad except that your milage takes a hit when you push it hard like that. I generally build up speed before the hill and let it bleed off some while climbing. I try to keep it under 2K most of the time even though I know that sometimes you have no choice but to run it up a little higher. If you're seeing 3.5-4K regularly on the highway, you're probably not getting the best milage from it.

 

The engine is designed to rev to the most efficient RPM that will meet your torque requirement

In other words, if you are requesting more torque than the engine can provide without "lugging" it will indeed rev to a higher RPM. The only thing you can do to prevent this is request less torque ... i.e. ease up on the pedal.

 

...and if you're using it, turn off the cruise control. While on level surfaces, you're better off using the CC to keep your speed constant to get good MPGs, in hilly areas, it's a bad idea, as the CC requests more power from the engine than actually needed.