Prius II Battery

shouldn't drop that much, give it a few more tankfulls. seeing a lot of newbies with used pri and mileage problems. when you start the car in the morning it should be about the same but may drop quickly during warm up.

 

It is impossible to accurately judge gas mileage on individual fill-ups. The gas tank uses a bladder that makes it impossible to get accurate pump shut-offs. I keep track of both per tank milage as well as the mileage that the MFD shows and find the kind of variations that you encountered - while the MFD display milage is more consistant (on average I find my MFD reads about 2% high).

 

No it is not normal to drop a significant amount of SOC (state of charge) overnight. Here I'm assuming that you mean that the charge is gone as soon as you put the car into "ready" mode but before you actually drive it.

If however you mean that the car drops a few SOC bars soon after you start driving it then yes this is absolutely normal. This occurs because the prius will preferentially use electric power while the engine warms up. Even though the engine is running it's basically just idling while the electric motors do all the real work. So in the first one minute of operation it can use lots of battery power. You can minimize this by either letting it warm up (idle) for 30-50 seconds or by driving very slowly at minimum power for the first 30-50 seconds (with engine running of course).

This is simply due to the fact that the amount of fuel used is not known accurately enough. You have to measure total miles travelled and total fuel pumpped over several weeks to really get a good "pump calculated" MPG estimate. The reality is that you're probably getting about 40 MPG and on the first caculation you under-estimated the fuel used (I mean actually used as opposed to what was pumped, because you never really know exactly how much is left in the tank) and on the second caculation you over-estimated the fuel used.