MPG Dropping

it's probably the tyres. did you get low rolling resistance? if it's not the gyres, it might be a bad 12 volt battery. welcome to priuschat!

 

You tires are not LRR and they also need a break-in period. I suggest you try 38/36 or even 40/38. Those pressures will probably increase your mpg somewhat.

 

4-5,000 miles. no guarantee they will improve tho.

 

5000 miles to break in tires?

Should be done by 500

I'm sure a 20% drop from changing tires is a little excessive?

 

that's why i would check the 12v.

 

no, the 12 volt starts the cars computers when you power up. it's in the hatch, right fender.

 

put a digital voltmeter on it in the morning before starting the car. if it's under 12.4 volts, pick up an oem at toyota and replace it. 2010's are notorious for 12v problems, and having work done on your car (new tyres) can exacerbate it because they leave the door open while working, the dome lite stays on and drains the battery.

 

yes, when the 12v is low/bad, the hybrid battery keeps charging it, leading to the ice recharging the hybrid battery more which lowers your mpg's.

 

I would guess tires, check side walls on tires for max psi settings. My tires are at 44 psi front and 42 psi rear.
Do not inflate over max psi. Run 2 psi less in rears (Toyota recommends). You will get 3-5 MPG more.
Good luck!

 

if that doesn't help, let's revisit the battery.

 

personal preference, mine are 42/40, f/r. sometimes you have to weigh ride quality vs mpg's.

 

^ It's up to you. With the higher profile 15", even at 44 psi the ride's won't be too rough. Experiment. I'd say 40~. Going the extra 4 lb's to 44 isn't going to gain you signif mpg, and will impact the ride.