Same Prius, Not The Same MPG

You have done enough to prove that 'you' are not the problem. Go back to the dealer or another one and ask for Toyota customer relations manager. Every dealer shall have one on site. Have the dealer check the computer readouts. There are 7 computers in Prius. Document your findings and experiments well and in details. Let us know what happens.
Don't give up.

 

I'm curious about the results of usbseawolf2000's suggestions. I'm sure it's a pain to get together with your sister to keep doing side by side comparisons. Then see if the dealership or another one could be more helpful. Doesn't sound right.
Your sister drove, and the dealership drove your car when they rotated tires, so it can't be the parking brake partially on, right?

Did you feed the hamsters in the glove box?

Hope it's resolved quick.

edit: didn't see you took it back in...sounds like you're on the right track

 

Bad cell in the 12 volt battery would cause the charger to run at max continuously? With the added A/C load maybe no ICE shutdown? Not bad enough in voltage drop to cause an error code? Let us know what codes the shop reads.

Traced drop in mpg (20+%)in the Ford and Chevy to a bad 12v cell.

 

Unless you weight 400 pounds and she just 150...

 

EPA is not a guarantee. There may be unavoidable circumstances in your daily driving that prevent you from achieving EPA mileage and, yes, then you will need the special techniques to OBTAIN EPA estimates.

 

Beside would be okay, but "right behind" should result in better mileage for the trailing vehicle.

 

OK, how about one car length behind for every ten MPH for safety?
To really get much draft, you have to be stupid close to somebody, I did assume the OP is not stupid. Point is his mileage isn't even close, I don't think he is talking one or two MPG here, I think he is talking a rather large difference. Dealer agrees there is a problem, so this is moot anyway.

 

any news from the dealer?

 

Any updates?

 

Can you swap cars with her for awhile? Let her drive your car for a week.
I get low to mid 60's in city driving, but I'm the guy as you say is pissing everybody off. My wife has gotten as low as 44 MPG combined driving until I fussed at her and merely modifying her driving style slightly put her mileage into the mid 50's. I believe mileage is extremely sensitive to driving style. I'm certain that if I drove like most people on the road and accelerated into red lights and braked hard for every one so that I came to a complete stop just about the time it went green again, and then Bam back into the power section racing for the next red light, I'd be doing good to get 40 MPG too.
Thing is, I easily get much better mileage than my vehicles are rated at, I get 18 to 20 MPG in a one ton Dually C3500 PU for example. Driving style has a LOT to do with mileage. And no I don't P&G or use any other unusual driving techniques either, just try my best to conserve momentium is all

 

i can also get raging mileage as long as i'm driving local freeways. city driving can be tricky if you're into the mpg game. dont be afraid to accelerate ( NOT flooring it ) but get into the coast mode asap.

 

City 46 - 48
Highway ~ 55

I have added about 3-5 mpg per tank - maybe due to my learning and breaking in.


My average from the beginning is now 51.

I seem to be smack dab at the EPA numbers. I can have a hundered plus miles on a tank and still show 60+ mpg, but that is for one specific work commute. More miles and even a couple city errand hops and that number gravitates quickly back to my averages.

My tires are 42/40 and I try at good technique, but not obsessively and I am not afraid of the pwr area when needed for traffic or conditions.

 

Maybe stop trying to P&G so much, and just drive the car like your sister does?

 

Since both of you have Prius III, you should have 15" wheels. Do you have an after-market wheels?

Also do you have different tires? For ex: Bridgestone Ecopia

 

Ok, this sounds interesting:

• ICE problem - could the engine be running in an inefficient mode, say open-loop instead of closed loop trim ... valve advance issue ... EGR problem ...
• drag problem - transmission or wheels or brakes

Are you near a hill that is relatively free of traffic that you could do a roll-down test? If you could, please provide coordinates for the hill, say 15-20 m high, so we can use Google Earth to calculate altitude change and distance. For example:

34 36' 47.85" N 86 34' 20.40" W - 209 m
descends to 177 m headed west
​

I live in the Tennessee Valley on the edge of the Piedmont Plateau. Once we understand the altitude change, we can compare your hill roll test, the change in velocity, against our ZVW30 and possibly even your sister's car. Doing the hill roll test in "N" eliminates engine effects so if there is a drag problem, it should be obvious.

A hill of 15-20 m should be more than enough starting from dead stop. If you have a GPS, we can probably confirm the altitude change.

If all three cars show the same increase in velocity over the same drop in altitude, it eliminates a drag issue. We would next need a taller hill to run a hill climb test.

In a hill climb test, we use the same, speed to ascend a similar slope hill and measure the fuel consumption to reach the top. The car with the greatest fuel consumption has an engine and/or transaxle problem. Then comes the fun part ... figuring what it might be.

Bob Wilson

 

I'm having a very similar issue - but have waited a few weeks reading posts about driving, PSI etc. I have yet to get over 43mpg - and I'm driving easy - 65 freeway, gliding as I can, even using EV to ramp to 25. Nothing changes my mileage. Yesterday's freeway trip - 150 miles at an easy - no cruise, no hard acceleration, flat drive at 65, yielded 44mpg...

Please let us know what you find...

 

I certainly cannot speak for the Gen3 Pri, but my Gen2 will behave the very same way.... at times. I cannot always say why it does this but I figure there is some enviornmental variable that leads the intelligence of the system to make the decision it does.