Issue with MPG

I have a 2010 Prius and having an issue with my gas mileage. I tried everything but I can't get anything more than 42 mpg (display) at the pump is 2-3mpg lower. My car has 142000 miles.

Here's more information about the car:

I cleaned maf, map, egr. Oil is a synthetic 0w-20. Spark plugs changed by the previous owner with iridium @129k.

Brand new brakes front and back. No drag or sticking.

Accessory battery is from 2017.

It doesn't matter how I drive my gas mileage is around 40-42 and can't get anything better than this.

Before this car, I had a gen ii prius and I was getting around 48-52 with the best result of 61.


Not sure what to do or how to improve the mpg. Any suggestions?

 

My tire pressure is around 36psi.
I did inspect the EGR when I got the car 2 years ago. Everything looked clear, even the EGR cooler. I didn't pull the intake at that time.

I just order the PCV valve and intake gasket and I will be doing some work this weekend, along with tearing down the to EGR.

I just checked the wheels and they move freely. 4-5 revolution per spin.

As far as the brakes. the answer is no. I got this car @ 129k with a rear brakes issue and the car was getting 25mpg. Someone at the chain brake shop installed wrong brake pads. it resulted in horrible angled pad wear ( within 70 miles from the installation, brand new rotors and pads were shot). The chain store said that there is no warranty for the brake work, and most likely something is bend and they refused to work on the car. Former Owner went to the dealer and the dealer gave them a quote $3500 to replace every single component of the rear brakes.
This is when I came in and got the car. It took me 1 hour per wheel to hammer out brake pads from the brackets. Installed new rotors and pads and put everything together. 14k miles later everything is working good. The MPG went from 25 to 42, its been like that for the last 2 years.

I will do some work this weekend and I will report back.
Thank you for suggestions.

 

This past weekend I took the intake and EGR cooler off. The cooler wasn’t too dirty. Before cleaning I was able to see the light through it.
After multiple soaking and multiple rinses with the hose, it was clean. I was able to see the spikes in the fins, and all ports were open. I think the cooler was replaced in the past. It was way to clean to start with, and I end up with clean stainless steel metal on both ends.
Changed the PVC valve and intake gasket. Cleaned all EGR passages in the manifold.

Yesterday, I took the car for a 100mile trip and my mpg was around 45.5 ( reset at the beginning). The trip included mix driving where 60% was driving 55 mph. A little better.
Last night I added injector cleaner. When the intake was off I did inspect valves and everything looked pretty clean. So will see.

As far as maintenance, here is a list of things that were done in last 13k miles ( I got this car @130k, now is 143k):

- Replaced Engine Air Filter and Cabin Air Filter (Done @ 130k)
- Replaced 12V Battery (Done By Previous Owner. Battery is from 2017)
- Cleaned Hybrid battery Fan ( Not done will be doing this next weekend).
- Cleaned MAF and MAP (Done @ 130k).
- Changed Transmission Fluid ( Done @ 135k)
- Changed Engine coolant (Done @ 135k)
- Changed Inverter Coolant (Done @ 135k)
- Changed PCV valve & tube ( Done@ 143k)
- Changed Spark plugs (Done By Previous Owner Battery @126k)
- EGR cooler removal and cleaning, EGR tube cleaning ( Done@ 143k)
- Cleaned MAP (Done @ 143k).
- Intake manifold removal and cleaning ( Done@ 143k)
- Rear Brakes (Done @ 130k)
- Front Brakes - new pads (Done @ 130k)

I reset my trip every fill-up and I calculate manually every gas tank. mpg is as follow:
Winter – Display 34-38 mpg – at pump 29 – 35 mpg
Spring - Display 40-45 mpg – at pump 38 – 42 mpg ( rarely using AC)
Summer - Display 39-42 mpg – at pump 36 – 42 mpg (using AC)
Fall - Display 40-45 mpg – at pump 38 – 42 mpg ( rarely using AC)

The mpg at the pump is always 2-3 mpg lower than a displayed.

Before this one, I had a gen 2 and it was able to get 48-50mpg without trying too hard. With this one, without trying I will get 42 and with trying and annoying everybody I’m getting 44.

A few weeks ago I drove my friend 2016 Prius, and I was getting 55 mpg so I don’t think it’s my driving skills. Just saying.

 

** Update**

The car is fixed, and I'm getting 55-57 mpg on 88 octane gas (15% ethanol).

I replaced two things: spark plugs and a MAF sensor.

Spark plugs.
As I mentioned before, spark plugs were replaced by the previous owner at the local mechanic shop ( have paperwork). The spark plugs were Autolite iridium, and they looked terrible. Very bad corona at the base. And they were gapped to up 0.1". The average was 0.09". Yes, this is the correct number.
Installed new Denso spark plugs, gapped and the car is running better. A lot smoother. The transition between gas and electric not noticeable. The mpg went up around 2-3 mpg. I was getting 45-46mpg on the 100-mile trip.

MAF Sensor.
So, I was messing around with Elm327 and Car Scanner App, and I noticed that when the car is off, the MAF reading is negative (-0.25g/s) without any air flow.
I installed a new sensor from eBay. Current reading is -0.16g/s. The car was running fine. No change in the car operation. No change in car power. But a big improvement in mpg. First 100-mile trip; 55-57 mpg without really trying. Next 100-mile trip; hypermiling and grandpa driving and I was able to get mpg to 65 (display).

As far as MAF, I am not sure if the negative reading is normal for this engine. Can someone verify this?

At next fill up, I will put 87 gas to see If I can reach 70 mpg with hypermiling and grandpa driving .

I want to thank everyone for all their help and suggestions.