2010 prius, 31 mpg, Toyota doesn't care

Has less than 8000 miles. After 4000 miles and getting 48.6 mpg was going up slowly rising 1/2 mile hill when car suddenly surged almost all the way up the hill on its own (wasn't using cruise control) then just quit. Prior I was averaging 48.6 mpg calculated. The last 8 fillups have ranged from 31 mpg to 37 mpg calculated going the same trips as before. Taken to two dealers and they say theres nothing wrong with the car, that there's a air bladder in the gas tank thus barometric pressure is whats causing the different mpg and I shouldn't pay attention to mpgs as most prius are getting the same mpg. Also having trouble with ev system shutting off at 8mph coasting on a flat road with battery fully charged, dash message states going to fast. Dealer couldn't find nothing wrong with this either. Brakes squeek at times, dealer stated nothing wrong with that either. I have contacted Toyota "we care" 3 times, and am told somebody would get back to me in 24 hours. Doesn't happen. THEY DON"T CARE! I'm wondering if Toyota is giving dealers bonuses not to fix cars. By the the way, about 3 miles after I left the dealer I stopped at a store and a woman getting into a older Ford when I pulled up said, " Your car sounds sick, its making weird noises."

I cannot answer much, only these:

The 2004-2009 models do, but the 2010 does not.

Has the engine fully warmed up? If not, EV should cut off between 9 and 10 mph, with the 'too fast' warning.

If the engine is stone cold (below 68F), U.S. models won't go into EV at all.

As fuzzy1 said, the 2010 Prius ditched the bladder for a standard tank, so the dealers need to get up to speed on that and other differences the new model has! The EV button is pretty useless, a warmed up engine(after 20 or so minutes of driving) and full battery might get it to work. A check of several threads will reveal the Prius will suffer a big mpg drop in the winter months, so your numbers aren't that unusual especially for a state like Vermont! Come spring you should see the mpg back to normal. In the meantime check threads on grill blocking and engine block heaters, these can help, plus check tire pressure! The hill thing I dunno!

PS. The Prius makes odd noises compared to standard cars, so someone not used to hearing these cars might think somethings wrong with it!

The noise you hear after the car is turned off is the coolant being delivered to the heater core and canister. It's part of the HSD and it's very complicated. But if you hear the noise, that's a good thang!

31 mpg is not normal however and merits investigation.

My understanding is that the Generation 3 does not have a coolant canister, commonly refered to as a coolant thermos. They redesigned the whole coolant system the new generation has a heat reclamation system thus negating the existence of a coolant canister.

Correct, the 2010 has no bladder gas tank nor does it have the coolant thermos and its associated coolant heat storage pump.

For gas mileage help, please answer the questions at http://priuschat.com/forums/gen-iii...-answer-these-questions-esp-if-youre-new.html.

We need more info. I have no idea where in VT you are, but per History : Weather Underground, the temps have ranged from 15 F to 50 F w/an average of 26. Per History : Weather Underground, since your other post mentions 4 months ago, temps ranged from 42 to 87 F with an avg of 66 F. You WILL experience a mileage drop w/colder temps and if your drives are short and esp. if you use the heater, it will make it seem low.

Please also see the 3 links at http://priuschat.com/forums/gen-iii...ileage-in-mid-west-winters-2.html#post1216266. FWIW, http://www.consumerreports.org/cro/cars/new-cars/buying-advice/most-fuelefficient-cars-206/index.htm is what CR got in their testing.

Then what is the noise you hear after you turn off the gen III?

I don't have a Gen III but have test driven them a few times. It's likely the brake accumulator pump. One should be able to repro that sound by pumping the brake pedal a few times, even if the power is off. I was able to repro that sound by doing exactly that, after my last test drive (to confirm it's still present).

The thermos being ditched is mentioned at http://www.cleanmpg.com/forums/showthread.php?t=18752 and http://www.priusownersgroup.com/?p=6119, for example.

Hi Noexcuse,

One way to be sure your the car is working right, is to get it well warmed up, and take it on a steady 60 mph interstate cruise for an hour, on a low-wind sunny day, with dry roads. So this will take about 1 1/2 hours to complete Check your tire pressure before hand, set them to 42/40 psi.

Set the temperature to 65 in the car. No more.

Reset one of the trip odometers after the warm up.

After the one-hour test drive, at a steady, cruise control drive, out 30 miles and back 30 miles (to negate wind). If there is wind, its best to drive in a direction parrallel to the wind. Side winds create drag in both driving directions and will give poorer results. You should get 40 mpg plus between 0 and 10 F, 50 mpg plus at 20 F, and 60 mpg plus above 32 F.

Ah...(*) Welcome to Prius Chat! :welcome:
If you cannot achieve the mileages listed above then something may indeed be wrong with your G3....you were getting mid to upper 40's before this recent decrease, which indicates to me that your driving style leans more towards the 'normal' range than those used by the hypermilers out there---so I would expect your mileage to decrease somewhat during very cold weather, or while driving in high winds.

Regardless, if you think your car is not behaving properly, and your dealer (which doesn't seem to be very knowledgeable in G3's) cannot confirm that it is working properly to your satisfaction, then you need to switch dealers, and get a second opinion. Toyota also has a customer care branch out there that, with a little research, can be enlisted to help you resolve any dealer issues.

Good LUCK...
Let us know how it shakes out!

Thanks for all the good information from all of you. Nice to know about the bladder. Contacted service department at dealer and he said it does have a bladder in the fuel tank and by law it has to. My poor mpg also happened on warm days on same trips. The weather does not appear to be effecting mpg that much. The noises the lady referred to was when the car was still running. I will try to get back to each one of you. Thanks
so much.

The guy is an idiot.

From noexcuse: Ev use to shut off at 18 mph on flat with excessive speed alert and no heater and car warmed up. Now same flat, 8mph, and no accessories on.

was it heritage toyota?

From noexcuse: Thanks so much the reply. But vermont was not that cold when my problems all started and have continued. Two weeks ago I was in 50 degree weather and got same poor mileage. Also grill blocking might effect warranty issues when theres a problem even though it might not be related, a dealer could say you altered the car.

Those are odds speeds, they should be closer to 25 and 10 mph.

Also, it is important to know the engine coolant temperature, and this is where a ScanGauge or other engine monitor is crucial. When coolant temperature drops below the threshold while traveling, EV may cut out, and this will be highly weather dependent. So far I have witnessed this only at the 68F threshold between EV and no-EV, while parked. Because I don't use EV in actual driving, I haven't tested this for the 150-something threshold between 10 and 25 mph limits. But in this weather, in extended glides or traffic congestion, the engine often falls below that EV temperature requirement.

Short answer: don't use EV in most normal driving, as it rarely helps efficiency. Just use it for reparking movements where warming the engine is senseless.

From noexcuse: No it was dealers in White river and Montpilier

Thanks for the reply. I know the noises your talking about, but this sounds different and today brake warnings came on.

From noexcuse; Thankyou for the reply. The weather doesn't seem to make that much difference. Experimented for a week with heater on and off, no difference.

From no excuse; Thanks for the reply. I tried this when it was 50 plus degrees between Boston and Manchester, NH and back on a weekend on the interstate and very little traffic. I got under 40 mpg.