what am i doing wrong?

I didn't see the recommended economy till I had around 2,000km on the clock. I think it takes a while for you AND the car to settle in.

 

I run 42 PSI in all 4 tires. Make sure your battery vent isn't blocked by something.
It's on the left (drivers) side of the rear seat. Open the left rear door and double check it.
It needs to be unrestricted or the batteries will not cool off. Run the car in Eco mode
and turn the A/C down to 65° and see how things go. Also drop your speed to 64 MPH.
You should be able to get 46 MPG on the freeway at 64 mph with 42 psi, unless you have
lots of luggage/extra weight on board.

 

OK, what was your mileage in your last car at 70+mph in 90+ degree heat, heat and cold kill gas mileage but the prius, be it c or hatchback still shine, look at the numbers.
If you want an anti-gravity machine, go to sleep, dreams are great...

 

To be honest, yes, your expectations are simply too high for the given conditions.

I also achieve below EPA because my conditions do not match the testing conditions. However, I understand that my mileage suffers below EPA regardless of what car I'm driving.

On the occasions that I drive in better conditions, I can well exceed EPA ratings. In fact, I've achieved 67 mpg on a 100 mile round trip before. Just that my everyday route yields 44 mpg and I understand the parameters in which I'm driving usually

Galaxy Nexus ? 2

 

I'm the same. Our winters are fairly mild so I actually get my worst mileage in the summer and that's due to the AC. If you're concerned about mileage in the c and you're using air con, my top three suggestions are:

1. ECO Mode
2. ECO Mode
3. ECO Mode

And check your tyres. After you've selected ECO Mode.

I'm not kidding, if you're using AC and you're not using ECO Mode, it's going to cost you. If the car is hot when you first get in, put all the windows down for a couple of minutes to vent it down to ambient temps, then raise them and let the AC take over. It's still quite effective in ECO Mode but the car is much more sensible about how it uses it and this makes a huge difference.

 

indeed.. do not skimp out and bear with the heat inside the cabin without AC (but use ECO when you do)

the traction battery is inside the car.. and it performs better when it's properly cooled.. the engine on the other hand, likes the heat (obviously not to the point of overheating..) but anyway.. the hotter intake temperature will allow better mileage at the cost of power.

compensating that loss of power by pushing on the accelerator more to get the car up to speed faster will hurt mileage a little bit... it may anger other drivers around you, but take it easy on the throttle when you need to accelerate up to speed.

whenever i'm below 15 mph, i try to keep the ICE off.. so for example, when I'm accelerating from a stop, I focus on staying in EV until 15mph, and then fire the ICE to accelerate up to speed, from there trying to stay under the PWR zone on the HSI... (it's some advanced hypermiling technique or something I read about.. I don't remember any other details..)

then there's other techniques.. pulse and glide... drive with load (which is applicable to hills)... etc..

 

By the way hieuous, I did nearly the same highway run that you did (AC highest fan speed and LO temp setting, 72 mph, level flat highway, light traffic, did both ECO on and ECO off), and I got exactly 40 mpg. It's 93 degrees here instead of 103 degrees where you are, so your fuel economy should be just marginally lower. I seriously think that your car is performing exactly as it should. For comparison, my SUV would get 20 mpg under same conditions.

Anyway, Let us know what your lower-speed commute is like, so we can trouble shoot that, if you still want. My past two supermarket trips, in traffic and at lights, have been in 90+ degree weather, and my overall "hot summer" city commute is also around 40 mpg.

So, I'm really tempted to conclude that there's really nothing that you're doing wrong since it's extremely hot in Las Vegas...you guys are expected to hit 110 degrees every day for a few weeks.

What really kills my fuel economy is that with all the tourists being up, some of them act like they own the roads... So I gotta step on the gas harder. You're probably going through the same thing in your city travel. Oh well, safety over fuel economy for me.

(Did anybody actually read all that?)

 

Over riding the fan speed and temp settings will defeat the Eco modes control over the A/C.
In order for the Eco mode to reduce the A/C's impact, you need to have the Eco mode turned on.
Turn the A/C on using the auto button and set the temp to the desired setting and allow the climate
control system to control everything else. It also helps to use a higher setting to reduce A/C impact on MPG.
I typically use mine around 65° to 68° settings. Don't turn off the recirculation mode either.

 

Oh yeah but I curious to know just what the actual mpg figure would be, if I blasted the AC like that.

 

So your new mantra will be to drive normally, and think "No other gas powered car would do as well", right?

 

Safety first. Your savings in mileage aren't worth as much as the safety of yourself and everyone around you.

Now that you know your car is doing fine and capable of being great, you should consider going with the flow of traffic again.

And most of all, rejoice in the fact that 40mpg was disappointing to you

Galaxy Nexus ? 2

 

Even at highway speeds I would expect near 50, if you are only getting 40mpg or upper 30's in a Prius C, I'd take it to the dealer and advise that you're getting less than the mpg you expected and have them look at things, run a computer check to see if anything is happening.

 

Only one thing you need to focus on: a visit to the dealer is free for them to check an issue like this. Its better to have someone tell you its the temperature in person after checking it, a certified Toyota technician, than just assumptions here.

I would agree that in extreme heat like that you'll expect some efficiency loss, but how much is the question. A certified Toyota tech in your climate will be able to better assess other customer experiences and compare against yours.

Trust the experts!

 

The car is rated at 46 on the HWY... it's about right at 70 in normal weather.

 

This vehicle is rated 46 MPG @ "freeway speeds" Driving 70 or 80 MPH will result in a much lower MPG.
Taking it to the dealer will be a complete waste of valuable time. Drive it like it's a hybrid and the MPG figures will
return to a normal rated level. Drive it like you would a non hybrid, without the MPG feedback data and it will return
about 40 MPG. I know people that only get 36 MPG, because they drive like their hair is on fire and they swear
it's not them. So, it must be the car

The dealer can't look at the car and tell you if anything is happening, unless the system detects a fault and records the data. No fault lights on, equals no problems found at the dealer.
They might put you though a fuel consumption test, but I can guarantee the results will point at poor driver habits and high speed driving. Ask me how I know. I've done it to customers and they finally quit coming in for repairs that aren't available, because it's their poor driving habits that create the problem. Some people just can't accept the facts.

 

70-80 are not typical highway speeds... Hence not typical mileage returns.

Save your time and do something good with it. Like hug your car and leave a lipstick mark on the hood

Galaxy Nexus ? 2

 

Well, I have to say that 110 degree weather is rather foreign to me, I couldn't imagine living in it. 85 degrees is considered hot here.