Why is winter *highway* mpg so low?

[MavMeister25]

I typically drive 70 oh the highway and get around 40 mpg summer, 35 winter. 23 Lariat Ecoboost AWD 4k Tow.

With your EcoBoost? How is that possible? I don’t hear of people with hybrids who even get that high of mpg on highways in summer.

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[2lbgill]

I have a '23 hybrid, and drive a normal highway route of 180 miles @ 70-75 mpg. My average speed is around 74.

Did it today, first time in cold temps (28°F weather) and got 27 mpg. Normal is 35-36 over the summer months. Keep in mind tire pressure was ~40 on all four (just filled them prior to trip).

Curious why low temps effect the hybrid mpg so much? Heat being on shouldn't bring it down from where it is in the summer, as the engine is running 100% of the time at ~75 mph.

I don't think the Atkinsen engine is very efficient in cold weather. I have the same 23 hybrid and the same problem 43 warm weather and 32 cold.

 

[inline_five]

We actually did a study on this during my graduate class for my engineering PhD degree. Several factors,
1. the Atkinson cycle efficiency is directly related to ambient temp and engine temp. When ambient temp goes down, it reduces efficiency.
2. Wind tends to be stronger in winter. And drag is proportionate to v^2. so even slight increase, will increase drag a lot on highway
3. Your engine will stay in ICE mode longer when starting up to heat up. For shorter trips, you will see big drops on MPG too.

Interesting! Yes I know about big mpg drops during short trips. 100% expected.

I don't know where you learned to read charts. But looks like 20% drop
In general, to me.

Looks like Civic was the only one to ~20% drop.

• Dec 27: round trip with temps between 45° (going) and 55° (coming) 33 mpg
• Jan 26: Temp on my last trip was 25°. So 27/33 = 19% drop. So I guess close enough

So I guess temps below 30° really impact this engine and mpg. I'm really surprised it's this much.

MDX
12.8/14.3 = 11% drop

Odyssey
10.5/12.2 = 14% drop

Accord V6
10/11.1 = 10% drop

Element
9.8/11.6 = 16% drop

TSX
9.5/10.7 = 12% drop

RSX
9.1/10.3 = 12% drop

Accord L4
8.5/10.3 = 18% drop

Civic
5.9/7.5 = 22% drop

The Civic's normal 5.9/100 is around 39 mpg so that would be similar to the Maverick. I don't know how that data was gathered - was it stop/go combined driving or purely highway? Who knows.

MPG drop in the winter is certainly expected if one does lots of very short trips.

 

[inline_five]

If this is a sample size of one trip that's not valid. You may have been driving into a wind.

Yes so far. Wind was around 2 mph headwind average.

Clearly you were either fighting a strong wind on the way there, or its at a much higher elevation than where you started from. Also unknown is at what speed? Aerodynamic drag is proportional to the square of the speed, so there is a huge increase in losses between going 60 and going 75.

So I was curious and looked this up. Departure was 270/04 so roughly 4 mph, arrival was calm 000/0 so average of 2 mph headwind throughout.

I did the same speed (within 4 mph) on all these trips. They are roundtrip with little additional driving except for the one on 5/7.

I basically fill up right before, and then drive round trip, and then fill up immediately afterwards. This is so I can track my pure highway MPG vs. my (mostly) city mpg.

I use cruise control the entire way basically 100% of the time since I'm traveling early am and get home late at night.

The one on 12/27 was done the fastest and was the coldest at around 40*

 

[The Real Maverick]

Didn't say heating drains the battery, but all those other things like heated seat ,steering wheel radio and fans does drain the battery, so you are driving in hybrid instead of electric.

Let me rephrase:

Seat heaters + steering wheel heater takes trivial power. Too little to matter. So use them as much as you like.

With both front seat heaters on plus steering wheel heater on it takes 7.33 hours to drain the hybrid battery one cycle. Just one seat heater and it takes 16 hours. And the hybrid battery will recharge that same amount in 2-3 MINUTES of downhill braking or 2-3 minutes of charging while idling.

Seat heaters cost you 1 cent per day and 0.001 MPG.

 

[The Real Maverick]

True story:
I had a Bolt EV.

In July, I had to charge mid-day.
It was 110°F outside.

So I plug in to a DC fast charger, and get back inside and sit in the car with the 1000 watt air conditioner running. The power cord supplies up to 150 kw.
But the Bolt can only suck 55 kW.

The CORD can give my battery 55 kW and send 1 kW to the air conditioner at the same time

Lady with same car pulls in the next stall. Attaches plug. Get's out lawn chair and umbrella and sits in the 110°F so she can charge her car with it off.

After 10 or so minutes, me sitting in my cool car drives her nuts. She taps on my window and makes the roll down gesture. So I do. She says

"Don't you know? Running the AC takes a lot of power and slows down the charging."

I politely say "no it does not slow down charging on these fast chargers. It only slows down charging on level 2 slow chargers."

(Level 2 only put out 6000 watts so you are siphoning 1000 of the 6000 and only 5000 watts will go to the battery.

I don't think she believed me, but the 110°F was uncomfortable to the point a few minutes later she was back in her car giving my way a try.

Your seat heaters take in the ballpark of 25 watts. Negligible. The HV battery can supply 25 watts for 16 continuous hours without the gasoline engine running.

 

[Prickly Pear]

Let me rephrase:

Seat heaters + steering wheel heater takes trivial power. Too little to matter. So use them as much as you like.

With both front seat heaters on plus steering wheel heater on it takes 7.33 hours to drain the hybrid battery one cycle. Just one seat heater and it takes 16 hours. And the hybrid battery will recharge that same amount in 2-3 MINUTES of downhill braking or 2-3 minutes of charging while idling.

Seat heaters cost you 1 cent per day and 0.001 MPG.

I run my seat and steering wheel heaters 100% of the time in the winter. I'm still getting ~44 mpg using winter gas and keeping my speed between 60-65 most of the time. I don't usually turn the heater on till the coolant is warmed up and cycle it to keep the windows clear.

 

[Tbone289]

Yes, there are summer blends and winter blends. I think the winter blend has more ethanol mixed in which will decrease your MPG. I'm sure there are other factors as well, but my winter mileage has always dropped on every car I've owned.

It varies from state to state, but typically it's the amount of butane in the mix that varies from summer to winter, not ethanol.

 

[npaladin2000]

I don't usually turn the heater on till the coolant is warmed up and cycle it to keep the windows clear.

Funny thing, the ACC in the Maverick will handle that for you pretty intelligently. The fan barely runs until the heater core actually warms up, then you can hear it speeding up.

 

[wb5oxq]

With your EcoBoost? How is that possible? I don’t hear of people with hybrids who even get that high of mpg on highways in summer.

 

[wb5oxq]

I typically drive 70 oh the highway and get around 40 mpg summer, 35 winter. 23 Lariat Ecoboost AWD 4k Tow.

Sometimes on shorter trips and in traffic where 60 is as fast as you can go I have seen mid 40s.

 

[MavMeister25]

I mean…not sure how your ecoboost is getting better mpg than a hybrid. I see the photo. I don’t get it.

 

[wb5oxq]

I mean…not sure how your ecoboost is getting better mpg than a hybrid. I see the photo. I don’t get it.

Hybrids get their best mileage in slower traffic where I only get mid 20s. I think the ecoboost engine is more efficient at higher speeds than the 2.5 non turbo engine which has to run continuously. My truck is also AWD and 4K tow both tend to lower mileage. The only way I get as low as 30mpg is if i drive 80+mph. The worst I ever average at 75 is mid 30s.

 

[wb5oxq]

Hybrids get their best mileage in slower traffic where I only get mid 20s. I think the ecoboost engine is more efficient at higher speeds than the 2.5 non turbo engine which has to run continuously. My truck is also AWD and 4K tow both tend to lower mileage. The only way I get as low as 30mpg is if i drive 80+mph. The worst I ever average at 75 is mid 30s.

I make a 90 mile round trip every Friday night on I35 and only use around 2.5 gallons of fuel at most.

 

[MakinDoForNow]

I run my seat and steering wheel heaters 100% of the time in the winter. I'm still getting ~44 mpg using winter gas and keeping my speed between 60-65 most of the time. I don't usually turn the heater on till the coolant is warmed up and cycle it to keep the windows clear.

The truck has a humidistat and the air circulates continuously at low speed through the floor vents. Anytime the temperature and humidity approaches the dew point the defroster is turned on which turns on the AC compressor to remove some of the humidity. If anyone in truck is panting or verbally active you may want to up fan speed one notch to increase amount of air through the defrost vent, which should not be necessary. I do not know for sure but expect the auxillary electric booster heater to come on and reheat the air the AC compressor has cooled down while removing the moisture. In my hybrid and they way I drive my electric miles almost stop at about 62 mph.

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