As I have learned on the forum it is best for gas mileage to keep the tachometer under 2000. I have notice while in the auto mode it jumps above the 2k reading...now once it does this if you lightly bring the gas pedal back the transmission will shift...kind of neat...only took me 28,000 miles to figure it out :-) takes a little foot coordination but once you do it you will do it forever! in sum the foot movement shifts the transmission around/above 2k...note that is if you are not in 7th gear already.

 

I've found that for accelerating, though, it's best to accelerate quickly. I suppose because it lets you get back to the lower RPM range sooner.