2007 Prius base milage

What was your previous car and what kind of mileage did you get with it? As others have said, it looks like you do quite a bit of regen. The regen isn't the bad part, but it can indicate that you're wasting fuel only to have to slam on your brakes. If you didn't get that great of mileage in your last car, your driving style might be partially to blame.

 

Has someone removed the original OEM Iridium Spark plugs from your Prius and replaced them with cheaper none iridium spark plugs? That may well account for the reduction in MPG.

The Prius 1.5 Litre Atkinson Cycle Engine was designed to use one of the following OEM Spark Plugs:

Denso: SK16R11
NGK: IFR 5A11

Anything else - especially NON IRIDIUM might (probably WILL) affect your MPG readings. You might want to get that checked out by a reputable dealer.

Iridium Spark Plugs obviously cost a lot more than ordinary spark plugs - some previous mechanic might have been trying to cut costs.
On the other hand, what's the mileage on the vehicle? Perhaps the originals were never changed out.

Remember, this car runs on standard fuel - don't put higher 97 or 98 octane premium fuels like Optimax or V-Power in it. Waste of money and a reduction in MPG. The engine is optimised for 95 octane (UK anyway). Depends what that is in your corner of the world.

 

What PSI do you have in the tires? I feel like there's something wrong with your car. I bet I could drive like a madman and still break 40MPG in my Prius.

 

That should be okay. I used to use Shell Regular, and I did get 66.0mpg using it last year. Then I switched over to a different fuel. I went for ESSO instead, and seemed to get better mileage out of that. So I've stuck with ESSO Fuels.

Here's another thought - what is the Ethanol content of that particular Shell Regular Fuel that you're using? Maybe it's actually 10% Ethanol content? That might affect your MPG too.

 

It's a bad idea if you think it will decrease your consumption. It will not and will shorten the life of your HV battery by causing it to cycle more often.

 

Have you checked the tire pressure yet? I can drive my Prius pretty hard and still exceed the EPA ratings with no mods besides LRR tires at 51PSI.

 

The aux battery report looks fine.

You might try increasing your tire pressure. Try 44 psi front, 42 psi in back.

39 mpg is better but it should be doing better still, especially in warm weather.

There is still quite a bit of regeneration in your last screen photo. Have you worked on finding that spot in the go-pedal stroke where the energy flow is zero (or close)? Use the energy flow screen to help find it. If you coast with the go-pedal all the way up, the car activates a certain amount of regenerative braking, slowing the car (and usually reducing fuel economy). For coasting (unless you're trying to slow down), you should be holding the go-pedal down a bit.

You might check your engine oil level to make sure the shop didn't overfill it. It usually only takes about 3.5 qts for an oil change, so it's easy to overfill.

 

And there's your problem right there methinks. I'm running my tyres presently at 40 psi front and 38 psi rear.
Methinks 36 psi isn't enough to give you higher MPG readings.
With this setting which I did within three miles of filling up with a fresh tank, I presently have 65.7mpg on my MFD (I got to 66.4mpg at one point after a run to work). I actually discovered that I have a slow leak in one of my tyres (rear right), and noticed this when the MPG of my new tank sank to 60mpg (in the first 3 miles) despite excellent hypermiling. I also noticed my tail wagging a bit during small course corrections and deceleration. Also, the engine screamed going up hills and and the vehicle wasn't so eager to transition to electrical propulsion mode.

So yeah, get those tyre pressures up, and you'll see a further rise in MPG pretty much guaranteed.