Bad MPG (25mpg) - New 12V battery - How do I test the Hybrid Battery with diagnostic?

Help. How can I know if Hybrid Battery is causing Poor Gas Mileage? I have a 2008 Prius with 130k miles and average 25 mpg in winter and 32 mpg in summer. Other Prius owners in my area are getting 40 and 50 mpg respectively. Thanks in advance!

- Have you read This Thead Yet? file:///C:/Users/Adam/Downloads/Why_Don't_I_Get_The_EPA_Mileage.pdf
yes
- What fuel economy are you getting and how are you determining fuel economy? (trip computer or manual calculations)
manual calculations, 26mpg average over past year
- What fuel economy are you expecting and why?
expecting at least 40mpg because it's a hybrid Prius
- What are the approximate outside air temps?
outside ranges from 20F in winter to 90F in hottest of summer.
- How long are your trips?
on average my trips are 5 to 10 miles (15 to 20 minutes)
How old is your 12v battery? What is the voltage reading of your 12v battery after sitting over night? (Method Here)
Replaced the 12v battery with brand new about 3 months ago hoping this would fix the mpg issue
Have you had your alignment checked? Any pulling or abnormal tire wear?
Yes. Alignment is good. No pulling or abnormal tire wear.
- How much of it is city vs. highway? Roughly what's the average speed in overall and and of each segment? Is there a lot of stop and go driving?
Mostly City driving, average speed is 40mph
- What's the terrain like of your drives? (e.g. flat, gentle hills, steep hills, etc.)
Combination. I live in flat but there are gentle and steep hills in any given trip.
- What are your tire pressures?
Tire pressures are set to recommended as per inside of driver's side door. (34 to 36 psi (?)
- Is your oil overfilled? (i.e. above the full mark on the dipstick)
Oil is less than full mark
- Make, model, year, engine and transmission of previous car? (e.g. 08 Honda Civic Si 2.0L 4 cylinder, manual transmission) What did you actually get on the same trips/commute? (Please give us actual numbers, not EPA ratings.)
Previous car(s) were 02' Subaru Forrester and I got 30-32mpg consistantly. Same with '06 Honda CRV
- What region/state are you in? (if you haven't set your location)
Western PA
- How are you trying to drive (e.g. trying to stay in electric only?) and how hard are you braking?
trying to stay in electric only
- What modes are you using, if any? "normal", EV, power, eco?
not sure of this. If there is a default in the 2008 Prius, that is what I am in.
- Are you "warming up" the ICE (internal combustion engine) by letting it idle after powering on?
Sometimes, but not usually
- Are you driving using D or B mode?
D
- HVAC settings? Are you using the heater, AC, auto mode, etc.? If using auto, what temp is it set to?
Heater is set between 68 to 75 in winter depending on climate, but NOT using Auto mode and I frequently will run it on medium to low or no.
- Are you using the factory tires and wheels? If not, please indicate tire make, model and size (e.g. Goodyear Assurance Fuel Max 185/65R15).
Not using Factory tires but same rims. It is cold and night now so I can report this later if anyone is interested.
- If reporting a mileage drop, did anything significant change on your car (e.g. accident, hit a curb or big pothole throwing off alignment, oil change/other maintenance/repairs, changed tires or wheels, etc.) or your commute?
Not reporting a mileage drop, this poor mpg performance has been an issue since I purchased the vehicle in August of 2014. Average only 25 mpg in winter and 32 mpg in summer.