Mileage under 40 on cross country trip

Even at 75mph I wouldn't expect mpg to drop that low but with the AC maxed it is possible. I hope you're not having an ECU problem like one of the other members.

 

Zach
I have a 2012 Prius C 2 also with 3700 miles on it and I am lucky to get 43 MPG around town> I live in a flat area with no hills so my mileage should be a lot better than it is. I was told by the dealer that I shouldn't worry until I get 5000 miles on the car??? I am still worried

I traded in my 2007 prius that always got 47 MPG no matter what, I could have saved 22K and kept my old prius... I have a feeling I have a problem with the car.

Rick

 

Driving 75 with the AC and getting 40, depending on elevation change, sounds totally possible without there being anything wrong with the car.

 

Rick- my guess is you're taking short trips. Try taking it out for a drive around town for a good half-hour, using basic hybrid-driving techniques. I'd bet you'll see a big change.

On the other hand- if you do drive around town for a half-hour and don't see a change there's a good chance there is something wrong.

 

Even with the new ECU I am still only getting about 46 MPG (which is better than 36MPG) but still not the mileage I was expecting. I traded in the 2010 expecting to up my gas mileage, but really it has come down and I am driving slower. That all being said the engine is still at only 1500 miles on mine and I expect things to improve once I get closer to the 5,000 mark once the pistons and rings have seated and everything has broken in properly.

 

Well I haven't taken any long trips yet and most of my driving is between towns up and down small hills. I fully expect my mpg to be lower than my current average but not that low.

On the other hand you are going 75 mpg, try going the speed limit and see what happens.

 

FYI - 75 is the speed limit in a lot of Midwest states

 

Hmmm...then go less than the speed limit and see what happens to your mpg. You get my point though?

 

Make absolutely sure you don't have the rear seat vent for the hybrid battery obstructed!

Edit: assuming vent is in the same location on the C as previous Pri.

 

This is a picture off the net showing the vent below the driver side rear passenger seat.

 

No one is forcing you or him to to drive 75mph. It is a limit not a minimum.

 

This is were the manual says the vent is. Be sure to very it does not have an obstructions.

 

Heavily loaded, cruise control on, driving fast, a/c blasting, probably windy at least some of the trip (c's hate wind.)

You're lucky you got that good of mpgs...

 

To add to the chorus, at 75 mph with the a/c running and the car fully loaded, results around 40 MPG is quite realistic.

What about the fuel, since you are now in a different location? The switch from pure gas to an ethanol blend would have an effect too.

Then there's the miles themselves. What did that do to the PSI in the tires?

 

I cut my tire pressure back from 40 psi to 36 psi all around to improve the ride (it works, BTW), and saw no drop in MPG on my 40 mile half highway-half non highway commute each day. But I was pretty shocked when the summer heat finally rolled in and at the effect on mpg of full time air conditioning use when temps get up into the high 80s, 90s or more.

Also, excessive use of cruise control, unless you are on fairly level ground most of the time, can actually give you worse mileage than if you were using some simple techniques like slowing a bit on uphills and coasting on the downs.

I have also found that 71 mph seems to be some kind of cut off speed, at least for my normal driving route. If I spend too much time above that, even a little bit above like 75, I struggle to keep the average mileage over 50. If I stay at or below 71, mileage in the low to mid 50s seem much easier to maintain.

Considering all the above, plus the extra weight, low 40s sounds about right. The battery vent could be a factor, also. But don't discount the air conditioning. Next time temps are in in the high 80s or 90s, and you're on the highway at 75mph with the air on, put the Energy Monitor on the dash display and watch to see how the ICE is doing almost all the work.



Bob

 

Pump up the tires again! You have much more weight in the car than your normal commute, so you are exacerbating the affect of the lower tire pressure.

 

I regularly drive multi-thousand mile journeys.

75mph in the Prius you are only getting the low CD effect, using 0 of the hybrid effect. 40's is what you will see. 42mpg to 48mpg on average. Going uphill or downhill (even slightly) has a big change. Going from 5200ft above sea level to 6800ft above sea level over ~80 miles changes the mpg from 50-55mpg at 75mph-100mph to 40mpg-45mpg at 75mph-100mph. Driving cross country you are going up and down, this will be measurable.

Using the AC at high speeds also is an extra burden and you will also notice that.

Add to that you are carrying a lot of extra cargo and weight, your mpg's seem realistic.

An SUV we have that drives around town and commutes highways (50/50 city/hwy) gets near 22mpg. When we drive it across country loaded, we get closer to 18mpg. That is an 18% drop in fuel economy. A 50mpg prius with a 18% drop in fuel economy will net 40.9mpg

Dropping fuel economy happens on all vehicles that are heavily loaded, going fast, have the AC on, lower tires (extra mass + lower pressure = bad), etc. The thing is you notice it more in the Prius. Yay for simple math.

 

Everybody always thinks that the "C" stands for compact...

It actually stands for "city".
If you want to get better mileage, change your driving or change cars.

Good Luck!