Just drive it. The mode doesn't matter. If you need more power just press the throttle more. You're not going to hurt the car by selecting different modes. A lot of us use an aftermarket device like Scangauge or Torque app to monitor vehicle systems.
Just filled up with 4.2 gals for 170 miles of driving a long streetch of highway that goes up and down gradually. Somewhere in the 40mpg range. A 6mpg hit with the MXM4 tires vers the Energy saver A/S. Dang it but I understand the MXM4 are a better tire? research time again but better late than not.
The "Tao of HSI" below is very informative as well: HSI The tip about switching to neutral on long glides is pretty useful too.
My findings so far are the same as Switch's. I'm still experimenting, but regardless of what the pros say, I am still finding better fuel economy when I am more aggressive on the accelerator for a short time than accelerating in ECO range for a longer time during the pulse portion of P&G. In my mind, if one is spending less time pulsing and more time gliding, the better the MPG will be. Then again, I only have about 1,000 miles driving experience in a Prius, probably 600 of that on the freeway. I will continue to experiment with different techniques until I get the high score. A bit OT: I've read here that the P&G technique doesn't work at freeway speed (obviously because the ICE is running), but has anyone found that using a similar technique works? Toward the tail end of my last trip to PA, I found that my MPG increased marginally when I accelerated to a bit over my desired speed (not exceeding the speed limit, of course ) and then let off of the accelerator until there is no bar or only a small wedge on the HSI until my speed dropped below the flow of traffic, and then did it again. I, of course, used gravity to my advantage on hills. Am I really saving fuel with this technique or driving my fiancee insane in vain?
P&G should work at highway speed for the most part. The ICE is spinning, but it's not consuming fuel when you're in the "warp stealth" situation. Personally I just can't stand having large variations in my speed even when there's no other cars on the road. I mostly stick to a variation on "driving with load." I've found that on the v-wagon HSI, 2 bars above the ICE cutover mark almost always gives me at least 50MPG instantaneous while allowing me to maintain a highway speed. I keep it there on flat areas. On uphills I'll increase the throttle input enough that I decelerate very slowly and on downhills I'll either go back to that 2-bars over the cutoff line (if I need to get a running start for the next hill) or just warp stealth/regen (depending on my speed/traffic).