Mpg keeps getting worse.

Some of the many ways the 12 volt battery fail can cause constant charging. If the 12 volt battery is under 12volts before you drive it for the day, replace it. (Currently the Toyota dealer has a replacement with a 84 month (prorated) warranty, that is as good as any) let us know the voltage before you start the car, and after it is running. A 2014 SHOULD be too early for 12 volt battery issues, but it has to be something.

 

The term "drag a brake" (autocorrect screwed it up) can mean:

1. Someone who 'rests' their foot on the brake pedal while driving.
2. Someone who has the parking brake partially set while driving.
3. Someone who has a defective brake assembly that is rubbing while driving.

All three of these conditions can be diagnosed by finding one or more wheel hubs being hot enough to burn ones fingers after a trip. Just lightly touch each hub. If they are all cool, no problem. If any of them are hot, there is a 'dragging brake'.

Bob Wilson

 

That one or more of the brakes is not releasing properly; it's like driving around with your foot on the brake all the time. Could be various causes, and a thorough brake inspection should resolve it. The most problematic would be if there's some sort of clogging inside the caliper, in the hydraulics.

Just noticed the question's been well addressed, oh well, will just add to the pile.

 

I just took off the Rhino Rack from the roof of my car....my mileage went up to 46+ and is still climbing....crazy how something like a rack will bring down the MPG.......

 

I once tried putting a bike rack on with two bikes. I could actually feel it dragging the car like a parachute, and I had to press the pedal harder to get it to accelerate. My MPG dropped from about 55 to 45.

Now I just put the bikes inside the car! (Removing the front wheels helps them fit.)

 

Inside also protects them better from weather, salt, theft, and accidents. Removing the front wheel is unnecesary with only one bike. Its bike-hauling capability is a primary reason I bought my Prius instead of any of the other candidates.

 

Agreed, I can fit one adult bike wheels on, but the second one I have to take the wheel off.

 

I highly doubt it is a hv battery. He stated the tires are new. Any time tires are replaced on a Prius they lower fuel economy until they get broken in. tire pressure even if it is just a few lbs low will also dramatically reduce fuel economy. A few basics is:

Check tire pressure
Check air filters
Check 12v battery (most commonly the cause of low mpg)

Cooler temps will cause a drop in mpg as well as hill climbing and windy days. Run a quality fuel system cleaner through the system with a tank of regular 87 no ethanol fuel.

My mpg had dropped into the low 30's and even though my 12v was still registering as "good" but needing a charge I had a lot of quirks and was smelling sulfur inside the car. Replaced the 12v and now my mileage has rebounded to 43.6 and still rising. Pri' do not like a weak 12v

 

such a sharp drop in mpg and progressive it getting worst? If it was brake drag tire pull I think you would have notice it since it your car! Either there a problem with ice or and hybrid assist system? Any error code? Present / prevouis ? Ice out of warranty! But the hybrid assist is still , how the cvt transmission working ? Does seem to rev higher rpm than normal? To pin point the problems need do process of elimination ! Find a well season Prius mechanic they will be able to pinpoint quickly! Good luck! Btw. Notice any loss in power?

 

are you running the ac in the car versus just the fan, the battery works fantastic when kept interior nice and cool. that is why they have air vents in the rear seat so the battery can escape the excess heat..

Posted via the PriusChat mobile app.

 

Long periods of idle with heater or air conditioner running will lower the mpg.

 

The original poster seems to have vanished almost 2-1/2 years ago and never told us what really happened.

 

As a Mechanic the Owner of a 2010 and 2015 I'd like to chime in on this. As vehicles wears out, so does it peak efficiency. Our 2015 with 28K miles gets way better mpg relative to the 2010 with 145K miles.