Wow - ambient external temperature REALLY matters for MPG

Yeah, probably some temperature threshold, shifts the car to a different warm up pattern. Where you've set cabin temperature will likely have an effect too: make the difference between engine running vs shutting down at lights, when it's partially warmed.

 

absolutely. 40 - 70 is a big change, and the corresponding mpg's make sense. the temp doesn't usually change that fast, so it's less obvious.

 

I get similar changes in fuel consumption with my Gen3 (relatively, of course... ). When the temp hits more than 10C/50F, the fuel consumption drops - not just the warm-up time and pattern changes, also there are more chances for the electric motor to do its job. Car heating has a huge impact too.

Here is what I got today commuting back to work, with even 2 warm up cycles (I stopped at a gas station to fuel up soon after leaving work) at 10C/50F, with A/C at 19C/66F and summer tires (Michelin Primacy 215/45R17):

That is, 11,25mi / 60mpg (with 6,2% MFD error, that is actually 56,7MPG) at 28mph average (a few traffic lights and a good stretch at constant 65km/h - 40mph speed).

 

Yes I notice this every spring. We have our first warm days and then my mpg goes up. Seasonal MPG changes are shown in the picture attached.

Also there is a very noticeable mpg reduction from running the air conditioner, about 5-10%. If you work that out it means the A/C consumes about 0.001 gallons/mile, at least in my climate.

 

I find that the mid 50's F is the tipping point. You also may be finished breaking in the tires and mechanicals. Climate control is also a contributor. In colder weather, I wear a coat and gloves. I never use heat and use AC only above 80F. Cracking the drivers front and passenger rear window a few inches each helps keep the interior temps from getting too unbearable in the warmer months..

 

This is true of all cars.
It is just more noticable when the MPG value is high to begin with.

 

Our 2010 Prius mpg increases at least 10-15 % when going from mid 40-s to mid 60's in temp. Last fillup was 55.6 mpg calculated for over a 500 mile tank warmer weather. Winter would have been 47-49 mpg calculated....

 

I seem to remember from high school chemistry that the speed of a chemical reaction roughly doubles for every 10 degrees Centigrade rise in temperature (18 degrees F). I would expect some change in battery performance in response to ambient temperature (though I'm sure that the heat generated by using the battery helps to mitigate this somewhat).

 

While higher temps yield better battery mpg, it kinda gets offset where I live... Got up to high 80s this week in LA and with my 1+ hour drive each way to/from work, I've had to use the AC so I don't melt... That dropped my mpg down, and didn't help that I was in a hurry the last couple of days and had to go 80/85mph to work and that and using the AC significantly put a dent in my mpg


iPhone ?

 

I hear ya on the AC. Our second vehicle is a black Jeep Grand Cherokee. With color and all the glass the AC runs constantly in the summer!

 

Has anyone actually 'plotted' their MPG-numbers versus mean-daily temperatures so as to SEE what affect temperatures have on their MPG-numbers?

 

For all you colder climate people out there. I learned a neat cold weather trick when I had my 2009 and it worked on my 2012 Prius also. If anybody interested. I will give a detailed explanation. Do not know if it would work on the 2016 Prius.

 

I run my AC almost every time I drive, even when it's cool outside. I don't like to open the windows because of all the dirt and dust in the air. It's so dry here. Also, I hope the cool cabin temp will keep the hybrid battery cooler? Anyway, I still average a steady 60 mpg.

Do you really drive 85 mph? I didn't think a Prius would go that fast!

 

85mph is just 137km/h, which is a regular speed on most EU highways (limit is 130km/h in most places).
The Prius can go up to 111mph/180kmh, and in Germany where I live, I have driven it as fast many times without any issues, even for longer stretches (e.g. 20-30 mins non stop).
Driving a Prius at 85mph is no big deal really as it holds the road really well.

 

I am all ears.
Why have you not tried this method on your 2016?

 

I found 160 kmh to be quite comfortable and just about right, However being as I was visiting, of course I drove my turbodiesel Golf mietwagen as fast as possible. It could achieve 215kmh. Fuel economy freak that I am, I kept track of distance and fuel use. For all the continuous full throttle use and high speeds (impossible here in the USA), I was amazed to get around 6.3l/100km, that would be 37mpg. I'd love to drive my 2016 Prius on the Autobahn.

 

I've never been to Europe. Why is there no speed limit on the Autobahn? It fries my nerves to just drive 75 on California freeways. People are crazy! I can't even comprehend reaching speeds of 100 mph or more, especially in a Prius? (Maybe on a closed, professional race track I could do it... If I was 25 again!!)

 

Drivers there are used to it, passing on the right is illegal, and they are very good at keeping right except to pass. One can move to the right with relative ease, but moving to the left lanes needs to be done with lots of caution. Just because one is going 110mph does not rule out some exotic car closing in from behind at another 90 mph faster! I absolutely loved it. Such fun, and such freedom!
BTW, my fastest stretch there was a few miles at 130mph, and that was in traffic (light traffic).