X15 Efficiency with auto: cruise control

I'm getting pretty sick of this cruise because it'll try to coast to the speed on the slightest of inclines, leaving you driving 4mph below the speed limit for half an hour. Is this just the way they are for pure efficiency, or is there a problem with mine?

Fuller Advantage 10 speed in a prostar

 

I don't get it. Sometimes it'll climb a hill at 100% keeping at the set speed, but sometimes it'll run partial throttle and keep dropping speed while it's fully capable of maintaining.

 

I was perfectly fine with my 10 speed as I knew exactly what gear I was in and what speed what sound was so it kept my attention. Autos are like trying to watch paint dry. Not exactly entertaining.

 

The company had full economy mode programmed, but scaled back on that. It's running much better, but far from perfect. I have a sample size of two, but both I and another driver are averaging 6.0mpg when a 10 speed got 6.2. They fell for the "automatics is better fuel economy" line.