Mileage down to 30.6 MPG!

When I changed my spark plugs, I got 7 more mpg on my 2006.

 

There's an abundance of info on these forums about what to look for, suggest you take the time to search and read up.
Tires/inflation, wrong oil, bad 12v batt and the list goes on. Often there's a combination of issues contributing.

The dealer won't do anything unless the car is throwing an error code. Good luck getting any action from them.

 

Please give us more information about your situation, by answering as much of this questionnaire as you can:

Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new

We can reply to a few things from your information already. You seem to have noticed the drop during winter. MPG varies seasonally, and in most climate zones is lowest in winter. New tires will temporarily cause reduced MPG until the tires break in. But if the new tires are not an LRR model, they will never get the same MPG of the originals.

Most of those are people driving the smaller and more efficient liftbacks and 'c' models. Your 'v' will always be lower.

Your very long commute is likely run at high speed, which also cuts MPG. Here is an MPG vs Speed chart for the Liftback.

But all these are not enough to explain the low MPG you are seeing now. So please fill out the questionnaire to provide us with more clues.

 

Have you checked the traction battery vent? It could be blocked, or the filter/fan could be dirty.

 

I do not see any Low Rolling Resistance BF Goodrich tires in your size.

 

Main reason your mpg is on the low side to begin with is your high speed. A choice you are free to make.

Main reasons for your drop in mpg: New, non-LRR tires and winter temps. Expect some recovery as tires wear in and as temps rise. Oil fill level and viscosity also possible factors.

If you don't have your own tire pressure gauge, buy one, and own that issue. Some 18 year old at the dealer who thinks 22 psi is cool could be costing you. Absolute minimum you should ever run is placard pressure on the driver door jamb. MPG will increase as you raise that pressure up toward the maximum spec of the tire sidewall. Play with that pressure range to see what you prefer. Ride is harsher, noisier, and vibrations worse at higher pressure. In every other respect, sidewall pressure is better.

Check the oil fill level. Each time you have the oil changed, check it again. Overfill is all too common. I suspect they could easily have used the wrong viscosity, even if they charged you extra for the good stuff (0W-20).

 

That's a red flag right there. The wrong tires could easily be costing you 3-6 MPG, and low pressure another 2-3.
17" low profile tires are hard to come by, there's only a few that truly offer LRR benefits. Whether its worth it at this point to justify replacing them is an open question that only you can answer, but at the very least you should pump them up to ~40psi. You'll see an immediate gain in MPG.

You replaced the tires around the same time that you noticed the drop in MPG.

 

Are you keeping track of every tank, so that refill variations can be averaged out?

Both extremes will cut MPG. So will any precipitation on the road, and any wind.

Best mpg should occur with dry roads, and the warmest temperature where you don't need AC.

12V battery problems are not likely on something this young. Many 2010 came with batteries from a bad batch, but this is uncommon

Speed is clearly an issue, a GenIII Liftback will barely do 40 mpg at 78 mph under ideal conditions (dry road, no heat/AC). Your 'v' will be lower, and won't even match your 2007.

Was you previous commute in the 2007 at the same speed?

Tsk tsk tsk. You should periodically check both of these yourself, don't trust the dealer. They have a different agenda than you, and best MPG is not on their list of concerns.

Check the tire pressure when it is morning cold. When highway warmed, it will be several pounds higher. If set when highway warm, it will end up too low.

Default is Normal, not ECO. But that can't explain what you are seeing.

Do get the model name, and verify the size.

Here is a list commonly of preferred Low Rolling Resistance tires. Non-LRR tires will cost some mpg.

Low Rolling Resistance replacement tires: Current List

 

Just looking at your timeline above, you had stated that in Feb your range was down from 400+ to 370. And that by mid-march it was down to 320-340. You also stated that you replaced the tires in March.

Mileage will be down pretty significantly in winter, which would account for the first observed drop. My understanding was it was a pretty rough winter in the NE, and lots of folks (Prius and non-hybrid alike) took larger than usual hits to mpg. The tire change could very reasonably account for the second drop. 14+ mpg drop would be a lot for just the tires, but not that unreasonable for tires and winter combined. You should be seeing some recovery as the temps come back up, but probably only about half of it if non-LRR tires part of the problem.

I know its tempting to believe that there must be something wrong with the Prius's "secret sauce" that must be causing this decrease, but the reality is its almost always something much more mundane. Even if there was some fluke degradation of the HV battery for example, it likely wouldn't even affect your mileage enough for you to notice. When the DOE did end-of-life testing on the original Gen 1 Prius, they found that even when losing 60+% of their battery capacity over time the vehicles were still operating within a few percent of their original mpg. The system just isn't that sensitive. Its not usually until its almost completely dead that you start to see the impact, at which point there are other symptoms.

The things people are suggesting above are the things that owners have found over millions of hours of collective "testing" experience that actually do impact mileage significantly. The overwhelming likelihood is that some combinations of those things is causing the noted drop.

 

As previously stated, your problem is likely a combination of factors. But tires and pressure are the most critical and account for the majority of your mileage drop. Believe it.

 

Look at the average temperature for the months you consider normal and the average temps after the mileage drop. Any difference? And was there snow/slush on the ground during the drop?

Has the mileage changed now that the weather is warmer? How much?

Have you measured the tire pressures in the morning after parking overnight? What were they?

Are you in an area where they reformulate the gas in the cold months? Does this affect your mileage?

And lastly, comparing a v to a hatchback gets you maybe 8-12 MPG difference (at least my son gets that on his 3 year old hatch versus my 2 year old v).

Hope you get back to what you consider acceptable.

 

The regular, liftback Prius, would probably get 5-10MPG better than your v/wagon in any given driving condition. Not sure why they directed you towards the v, its biggest advantages are rear seat headroom and cargo space.

Tires are where I would start checking, but your mileage loss seems a little too high for it to be just tires. Still, don't expect the dealer to put in the right pressure and don't expect it to stay at the right pressure between visits to the dealer.

 

Sara Hennessy - Lacking more data specifics from you, about your particular personal driving style, I do not think anything jumps out from your reported “dropped about 30%... calculated MPG of 29-31,” which indicates there is anything mechanically-functionally wrong with your v(vee). Depending on the characteristics of the particular non-LRR tire with which you replaced the OEM LRR tires, and their inflation PSI levels, running on non-OEM tires is good for a 4-6 MPG (10%-15%) “Hit” over the OEM LRRs. Additionally, comparing the on-board HSD-computer computed “Tank Range,” as displayed on the MID, against the hand-performed Per Tank-Full MPG calculations performed at your gasoline tank fill-ups, is a bit of “Apples & Oranges” MPG/Fuel Economy Data.

If you were/are looking for/expecting to see the same MPG-FE out of the larger-size, 1.8-Liter Powered mit HSD powering your v(vee) Station Wagon through a less fuel-efficiency friendly axle-ratio, as was delivered to you by your old iconic 1.5-Liter Power mit HSD GEN II/2G 2007 Sedan, you shall continue to be disappointed. If you were going for/pursuing High MPGs, you should have purchased the 2012 Prius c(cee) “ÜberFuel-Sipper,” which is powered by the same 1.5-Liter Power mit HSD hybrid propulsion system as the iconic GEN II/2G --- not the thirstier 2012 “Caddy In A Kimono” 1.8-Liter Powered mit HSD v(vee).

The Monroney Sticker on the 2012 v(vee) disclosed an EPA MPG of 44/42/40, and on the c(cee) it displayed an EPA MPG of 53/50/46, which shows that the c(cee) is typically 19% more fuel efficient.

QUESTIONS:

>> Is your driving style “Hybrid $mart,” or do you drive using a “Gas-To-Go/Brake-To-Stop” driving style?
>> Are you running in Normal, or with ECO or PWR (default Drive Mode is Normal, not ECO) selected as the Drive Mode?
>> Why did you leave your v(vee), which was still operating and drivable, at the dealer for a whole month, and what was the dealer doing to/with it to have to keep it there for a whole month?

As a comparative data point of one, me and my 2012 v(vee) Five [same Five Level as yours] --- my 2012 “V”onder “V”agon displays an HSD-computer calculated Lifetime Average MPG of 53.1. I drive "Hybrid $mart," run with my original OEM Toyo Proxes A20 P215/50R17s tires Up-Pressured to MAX “COLD” SIDEWALL PSI [51F/50R], and operate in ECO Mode staying in the “GREEN ZONE” 99% of the time. My Range XXX Miles + Trip A/B XXX.X Miles usually sum up to 540-570 miles, with this number occasionally summing up to 600-miles. I travel at cruise speeds not exceeding 70 MPH. I usually cruise at the 66 MPH "$weet $pot" when traveling on the Highway/Open-Road/Interstate.

IMHO, your "97% highway driving, @ average speed 75-78 MPH" is a key contributor to you falling short of the EPA 40 MPG-FE "Highway." FWIW FYI: When I cruise on the Interstate/Open-Road in my v(vee) Five at an electronic cruise controlled set speed of 66-70'ish MPH, over the 200-miles I-95 Interstate run from here on the Space Coast-To-Jacksonville, FL, I typically have 46-48 MPG-FE average fuel economies displayed on the instrument panel readout at the end of those 200-miles.

 

Have the dealer check mass air flow (MAF) sensor and wheel bearing or brake drag.