New Prius Owner ...

Note that there is no Toyota prescribed maintenance for the HV battery. It could fail at any time. Assuming it meets all the criteria, you should be covered under the 10 year/150K mile warranty. If you haven't already, I would get confirmation of your HV battery warranty coverage.

Given the fact that you're all in-town driving with heavy A/C use in a hot climate, 40mpg doesn't sound bad to me. I'm pretty happy with 40-42 in AZ with A/C set for 76-78°F. Note that the fuel bladder in the tank prevents accurate per-tank computations. It's best to average over at least a few tanks. Any reduction in computed mileage should be confirmed by a change in the reported mileage on the MFD.

I encourage you to conduct the discharge test in my signature to get an idea of your battery health.

Personally, I wouldn't sweat the 12V if it's working. Others may disagree.

 

Congrats...the 12v is in your living space in the back so you want a small vented AGM type battery, preferably the approved type for Prius. We don't know what you got but if it's a regular lead acid battery you really do not want to live with odors in the car and possible burping of the acid water.

 

I liked my Michelin Energy Saver A/S I got at Sams Club (there is both a Sams Club and a Costco in the same mall in Palm Desert, about 20 miles away) I would expect a 5 MPG bump.

Your Sams Club has a limited selection in stock, of those available I would choose Goodyear Assurance Fuel Max - 185/65R15 88H - Sam's Club
Your Costco has an even more limited selection in stock but I like Find a Costco warehouse- Costco
more than I like the goodyear.

There are no electrical reasons to worry about your current battery, only safety reasons (5 gallons of Sulfuric acid in the passenger compartment with no way to vent fumes out)

 

congrats and welcome! may the force be with you.

 

And fumes only occur with rapid or excessive over-charge. The 12V load is very low, and the Prius is pretty gentle with its recharge. Vent-hosed VRLA (AGM or Gel) is best, regular VRLA is next best, but I wouldn't give much concern to properly mounted flooded cell either. Of course, I have a heavily used flooded cell in my home office, so my standards are pretty low.

 

If it helps, Sam's Club and Costco are diagonally across from each other at the intersection of Dinah Shore and Monterey, just off the 10 Freeway. They're both visible from the freeway. I stop at one or the other for the "dog and a drink" deal with friends after golf outings every summer.

The mileage seems about right but you might see a healthy jump in mpg with new tires and a little more experience driving the Prius. Most of the main streets have speed limits (40-55) and distance between signals that fit right into the car's sweet spot.

 

You might want to keep an eye on the "resting" voltage of the 12V battery (car off after sitting overnight). A healthy battery will be in the 12.8V range, a poor one in the 12.0 range. A poor 12V battery may affect your mpg, constantly asking for energy from the hybrid system.

Some are cavalier about not having a correctly vented AGM battery in the cabin of the Prius. It's a safety decision you should be aware of.

Note that the presence of a non-Toyota battery likely means that not all maintenance was done by the dealer.

What's your tire inflation?

Check for coolant service (engine and transaxle) in the dealer service records. Also check for brake fluid flush. All should have been done by now.

Change the PCV valve when you do the plugs. Clean the throttle body and the MAF sensor, too.

Sometime in the mid 100,000s, many of these cars start consuming oil, so keep an eye on that dipstick.

Enjoy the car!

 

If anything, you're getting off easy: AC use for sure will impact mpg; this has always been the case. Someone may come along, say the Prius' AC is different, doesn't impact mpg, but really: there's no free lunch.

Someone else may say yes but: you need to use AC through the summer, to keep your hybrid battery cool. I've monitored the battery's temp with/without AC use, and see no significant difference.

Regarding the tires, yeah: running year 'round on generic snow tires: there is room for improvement. Not sure what to recommend in stock second gen two size. You could enter your vehicle on TireRack site, and specify to show only Low Rolling Resistance tires. Keep in mind LRR is not black and white, there are a lot of gradations, and a few that don't even deserve the classification. So read up, ask questions. Maybe Bridgestone Ecopia EP422 Plus, or Michelin Energy Saver A/S, if they're available in your size?