Ways to improve mpg

Redline the fuel system regularly. What’s the mileage on the 09? spark plug replacement ( iridium tiped) after every 60,000

 

If you are not mechanically inclined and near Dallas stop in at Texas Hybrids, get a diagnosis on the condition of the HV battery, as well as check the HV battery exhaust fan. Order a OBDII blue tooth reader and Dr Prius App, Hybrid Assistant.

Hybrid battery diagnostic and repair tool for Toyota and Lexus (priusapp.com)
Hybrid Assistant: App

Or swap a Projectlithium upgrade for 50mpg plus
https://projectlithium.com/?ref=9qLPw

 

congrats and welcome!

congrats and welcome!
at 233k, you're overdue for so many things.

unfortunately, the car won't give you a trouble light for many things that affect mpg's.

what you can control: speed, acceleration, hvac use, pulse and glide driving technique, avoide short trips and consolidate if possible, window tinting and shades, LRR tires.

clean the hv cooling fan, throttle body and maf, injectors.

measure oil usage

track mpg's by the tankful, calculated at the pump

all the best!
check brakes for dragging

change cabin filter

 

Gen2 of course is bad MPG during first 5-10 minutes until the hybrid system gets into warmed-up stage 5 or whatever..
You should be able to get 50 MPG after the warm-up on say highway going 55MPH. If not then I'd wonder the tires are the OEM diameter or other "major" issues.

I seriously think our newer 2020 RAV4 hybrid gets better MPG (40) than our prior Gen2 Prius around town because Toyota seems to have conquered the cold engine MPG issue that Gen2 shows. However, when we had a longer daily work commute, the Gen2 could do 50 MPG no probs. Much depends on trip length. Short trips were the bane of Gen2.

 

Summer weather in TX is hard on mpg especially with an aged battery.

Getting away with doing less than all of the scheduled maintenance on a 2009 Prius with 233k is insanity but also testimony to the greatness of the mechanical design of the car. Hopefully the oils and all other fluids have been changed regularly. If not, do them now.

Bite the bullet and change the plugs with genuine Toyota plugs obtained from a local Toyota dealer along with the PCV valve and serpentine belt.

 

Ac reduces mpg but is essential for an air cooled battery in 105f weather. Cleaning the battery fan and intake is almost never done. Most don't know it exists. If the battery overheats it will reduce capacity.

Driving over 60 mph kills mpg. Sitting with the ac on in Ready checking your phone kills mpg.

An aging hv battery absolutely kills mpg. The engine runs more because the battery capacity is compromised reducing regen storage and capacity. Fast acceleration hurts; quick last minute braking reduces mpg. These items are usually the most common causes.

In isolated cases, a bad 12v can Ready the car but cause excessive charging current, significantly reducing mpg. In this case a new 12v resolves the issue but this is rare. Have the 12v battery load tested.

 

No need to disconnect 12v when changing sparks

 

OEM plugs replacement interval is 120k miles. When replacing plugs, the PCV valve is right there and easy to swap.
If PCV is starting to go it can cause major problems on oil consumption.
The serpentine belt is another stealth catastrophe. From the outside it is typically not easy to see problems unless the belt is really bad. But when you take it off and look at the underside after 100k miles, it is often cracked badly.
In your TX heat, I’d imagine that’s the case.
Remember, you’ve got a great car, maintain it and enjoy it for another 200k miles.

 

Downstream O2 sensor pressure relief...

 

the app can read some codes, mostly battery it will tell you battery module voltages and estimated life remaining.
you don't need a code reader until you have trouble lights, then you might need a good one, or might not

 

I would do the serpentine belt and OEM Sprk plug from toyota ASAP.2009 prius serpentine belt replacement - Google Search Make sure the Air filter is new and clean Cabin air filter as well. I buy my filters at Walmart cheaper than anywhere else. Dealership has plugs for $9.00 online at olathetoyota in KS. see if your local dealer will price match. Watch a you toob video on replacing spark plugs with another friends.. 3 times in a row.
2009 prius spark plug replacement - Google Search are minimal and its any easy job if you can follow directions. Watch another video about cleaning the MAF sensor with the correct MAF spray fromhttps://http://www.googleadservices.com/pagead/aclk?sa=L&ai=DChcSEwisrqjKvLT_AhVU3cgKHecCBTcYABAJGgJxdQ&ohost=www.google.com&cid=CAESa-D2zjfxIn19nn2rx-3YtTqSg-XE5oicis38iuYQoG0b4MCTIR0o7Emf7W5FFlwT77N9Fr2Q4fUfFG4BorPYun3xnQAMWUzvrc1i1esn0Z629t5y0_uFd6L-u2c1QIgEJIQTD8PIb2G-Kjb9&sig=AOD64_2X3Fqs3_om4357ir09stxRes-BaQ&ctype=46&q=&ved=2ahUKEwjJvKDKvLT_AhV3FVkFHRCrAlgQ9aACKAB6BAgEEBM&adurl= Wal mart..Don't use anything else.

Every 5th fill up buy high end 91 or 93 octane gas. Watch another video on cleaning your throttle body without removing it. Also not hard. Watch lots of videos and take notes. Then when you do it yourself take pictures as you go. Makes it easier when you reassemble. Has your invertor pump ever been replaced? They last about 100k and are well worth going OEM. IMHO. $175 for that part (less online).

Again watch a video and earn. You can do it....we can help.

 

The inverter pump is a ticking time bomb....IMHO. If you can afford a tow truck to get you from wherever you breakdown to your house and then a ride to the dealership to get the part...then cool. My last tow (6 miles) was $230. My wife's died on her commute home. 5 miles from the house...She limped home in 85 degree heat with the hybrid fan on high and the RTOD.. I knew exactly what it was...Drive my Prius to the dealership paid $173 for the new pump and swapped it out that night in about an hour. I used plastic hose pinch clamps so didn't lose much pink fluid . She had to go to work the rest of the week and we can't have any downtime. After that mess. I ordered a new second OEM pump from Olathe Toyota in KS for $130 and swapped mine out because I knew it was the original and it would die....probably when I really needed my car. Just my .02 Maybe at least have the part on hand so when it happens you will be ready. Supply chain issues make waiting for parts.....crappy.

 

No, you can't really see much useful data from that screenshot. You are only drawing 1.24 A which is nothing. Having said that the bars exaggerate the extent of the difference between the highest bar and the lowest bar (which is 0.08 V) due to the dynamic setting of the Y plot of the graph. The voltage difference is not statistically useful.

You need to do an acceleration and deceleration test (not sure if the free version will do that) to get meaningful data.

Delta SoC should be 0%

The only other weird thing is your temperature readings which are nonsensical and possibly indicate a broken wire on the temperature sensor harness.