Newly 2010 Prius Owner 40MPG

check in with houston hometown hybrids

 

To not muddy the waters, maybe fugedabout miles-per-tank and distance-to-empty, stick to calc'd tanks.

 

Eco mode is more for rubber band pedal (keeping you at lower rpm near peak bsfc on the graph) and reducing energy consumption of the AC system during summer. Cranks the fan up to optimal and reduces the ac compressor duty cycle to optimal. So max efficiency. It does make it noisy and less premium-feeling though.
Air is thicker during the winter and the car has a hard time staying warm enough to shut off and reach max efficiency. So expect around 10% lower mpg during the winter.
The best advice is to make a point to use the regen brakes only and not get into the mechanical brakes (this was my mistake when i first got a Prius), try and use the heat as little as possible and see if mpg goes up. Around town the car struggles to maintain temp so i use heat as little as possible. If you venture on to 45mph+ where the engine isn't shutting off then you will have plenty of heat though. For me during the winter the first 5-10 minutes is always waiting for the car to hit 150F water temp and then it starts to get better gas mileage.
Of course you're due for all of the maintenance but start with putting 40psi in all of the tires and lubing the brake sliding pins front and rear.
I wouldn't worry about the HV battery until you start getting codes or check hybrid system messages but that is just me.