Why mileage gets worse in winter

Being my first Prius and my dealer didn't even know how to make my Running lights WORK. (I had to program it on the touch screen to come on) Can you tell me or give me a thread to learn how to (Push the Button) when to go into EV Mode and Power Mode. Reading your part about winter driving. I Changed tires to the Michelin Defender and winter weather hit all at the same time. (Now I'm learning about the Michelin AS (Why didn't my Discount Tire Rep know about this tire? I love my 2013 Prius 2 was getting 60+ mpg now down to 52 mpg. Thanks for helping.

 

The weather could at least partially explain your mpg drop (as you mentioned in the Defenders thread). Maybe they'll bounce back.

 

OK I see 2 threads now. In relation to this one. I tried an experiment today. Went 20 miles or so in town driving with the HEATER OFF. Temps in the 40's. Everything OFF. and I was able to pull 55 mpg according to the Prius computer for that short trip. As stated I will check my TANK mpg and see how much I dropped. Thanks again

 

Love the defenders! I know Michelin makes an LRR (low roll resistant) tire it's pretty affordable. They would be better at the pump but I imagine the Defenders will be better driving.

 

Defenders sport the GreenX label, fwiw. I'm sure they're not as good as Energy Saver, but maybe a good all-round choice.

 

We just had that discussion while we were out today. Our only vehicle was the Tundra 16-22 MPG depending on towing/city/hwy. Our goal was milage with the Prius. (Second vehicle now to drive) ANYTHING over 50 is GREAT! So if we loose a little with the Defender, we noticed it was quieter, softer ride and in the mountains here it's still FUN on the corners . . Who da thunk a Prius would be fun on corners and hairpin turns . . lol

 

My '08 mpg dropped in winter to low 40s from high 40s in summer. The '13 has better mileage than the 08 in summer--about 55 mpg.
I suspect it's the type of driving between fillups and outside temp that determines mileage. Cold starting below 50 deg and short trips really cuts into mileage. You make a return trip home with warmer engine, and mileage improves. You drive on the highway, mileage improves.

I'd like to hear more about the heater affecting gas mileage. I never noticed that in the '08. Different setup?
I set the temp to 65 now. The next lowest says "low". What does that mean? Does the air conditioner come on if the temp is higher? I'll have to check the manual.

 

How do you turn heater off? I just change "temp". Lowest setting is "low". next higher is 65. I use 65. But for short trips, no heater makes sense. Can you still have the blower (vent) on and the heater off?

 

My recollection is Defenders are very long wearing, but mileage isn't as good as the LRR Michelin. I have had Bridgestone Ecopias on my '08 and also on the '13. Good value tire for the Prius.

 

Follow up Mileage report (2013 Prius II) Winter Driving (Heater on 68') and New Defender tires. (Driving 60-65mph) From The Hills of Tennessee to Northern Ohio. Loaded with Presents, 47 mpg Going Coming back 40 mpg (ughhhh) We were loaded with presents etc. Temp set a little higher 70' (Driving 65~70mph The posted Speed limit) and I really believe we had a BAD HEAD WIND as it was moving my little Prius all over the place. But as was stated, if I took the Tundra, it would have been half that so I guess I'm NOT Complaining. $29 to go $33 (with almost a full tank left ~ one bar down) to return. $62 for the trip ! I'm GOOD ! Soooo if I want to get analytical I can try the next trip, with the lower temperatures and slower speed limit to see if I gain that 7 mpg back . . . hahahaha I can't control that head wind we had. Happy New Year !

 

Check my latest update from a trip in Cold weather with new defenders. Add in a Head wind on the return trip

 

I set the temp to Low starting cold from the garage. Eco mode. Blower at lowest setting - one bar. still some air flow. can't turn it off?
Then I set temp to 65 after car warms up a few miles. Outside temp in 30s. Some highway, mostly short trips. after 100 miles, I'm getting 49 mpg. With more highway, I should be around 50 mpg. I'd be at 40-45mpg with the '08 Prius2. 10-15% better mileage with Prius3 in eco mode.

 

New to the forum. Just purchased a 2012 Prius One.
I have experience with fuel economy with my Honda Insight Gen 1. There are a couple of factors that cause fuel efficiency declines in winter.

• Winter Fuel Mix
  • Most places add ethanol to fuel in winter, ethanol has fewer BTU per Gallon. (20% ethanol mix is about 93% of the energy of pure gasoline.)
• It's darker
  • You use your lights more often, that power has to come from somewhere.
• It's wetter
  • Water on the road increases resistance to rolling, and you use the wipers.
• Winter tires
  • Nowhere near as efficient as summer tires in rolling resistance.
• It's colder
  • You run the heater/defogger
  • Your coolant system has to warm up more
  • your fuel is colder
  • your air intake is colder.

 

FOLLOW UP MILEAGE REPORT : 2013 Prius II Michelin Defenders with a few thousand miles now on the tires AND . . we have had 60's here in the mountains. I am back up to over 50MPG (YEAH! ! ! 57 on our normal trip in to the PARK ) so no heater running or on low 66', tires starting to wear in I'm a HAPPY CAMPER !

 

If you haven't figured it out yet, there's an OFF button, highlighted:



What I would like to see is a way to bring the system back on, without everything being reset by pushing the AUTO button. For example, you can push the fan speed up button, and that wakes it up, with all settings as per before, but locks fan speed. Maybe pushing TEMP up once, would be the most benign work-around.

 

* Most places now add ethanol year-round. Unless they add more in winter -- unlikely unless they are violating the disclosure label on the pump, as most already have the maximum in other seasons too -- this will have no impact anymore.

* Winter fuel blends had lower energy content even before ethanol was added. This was a consequence of seasonal vapor pressure requirements -- higher in winter to allow reasonable cold starting, lower in summer to reduce evaporative emissions and vapor lock.

 

Assuming ethanol stays close to constant year 'round, what are the difference of "Winter Fuel Mix"; is there something else that's reformulated? Octane shifted, different composition to the gas somehow?

Ok, answering my own question, asked Mr. Google. One summary, something about higher summer temperatures requiring the gas to resist evaporation better, needing lower Reed Vapor Pressure (RVP).

What’s the Difference Between Winter Blend and Summer Blend Gasoline? | Fuel Up BLOG | Atlas Oil

 

Very true, most are higher E levels in winter. Depends on the distributor. There is a way to measure E content, requires a test flask and water.

The big thing is that you have always lost the MPG in winter. But you didn't notice it when it was 1MPG out of 20. It's 3MPG out of 60 now.

 

It is typical that in cold conditions mileage gets worse, lots of heat dissipates from engine + heater is working adding more energy consumption

 

Not to mention:
(1) lubes are thicker
(2) Tire rolling resistance is higher in cold weather
(3) Hybrid battery is colder in winter
(4) many other factors I forgot
(5) warm-up longer (we all have California-tuned Prius that are worse when cold than say a non-CARB FORD hybrid)

Winter gaso is about 2% less energy/MPG