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Mileage Curiosity

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Okay, here's the deal.  I have a 2016 F-150 4X4 3.5L Ecoboost, Supercrew cab with short 5.5' box. I noticed last year that I was getting somewhat worse mileage in the winter, but I never really got to compare any valid numbers.  Last week I had to drive to Denver (150 miles) and back on a day when the temperature was near 70°, and the truck's computer calculated mileage was 19.2 mpg.  Today I made the same exact trip, only when I left the house it was only 10°, and didn't get up to 30° until I was almost to my destination.  The mileage for that half of the trip was just 15.7. 

 

After taking care of the appointment I had, I headed straight home.  The temperature was up to 43°, and climbed to near 50° by the time I got home.  The computer showed an average of 18.1 as I pulled into the garage.  That seems to indicate nearly a 2.5 mpg difference for just under a 40° rise in temperature.  I know better than to take those mileage numbers as a real world quantity (My actual calculated mileage in summer driving was 18.5 mpg), but as a comparison with each other, they should be valid.  All driving was consistent, no hotrodding, cruise set at 80 mph all the time on the interstate.

 

Just curious if any mechanics out there can explain the reason for the significant increase in mileage as the temperature goes up.

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I understand there are winter and summer blends of gasoline. I have no idea what the difference is but I do know people complain about lower MPG with the winter blend. 

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What were the winds like during these trips? 70 degrees in the winter often suggests a strong Southerly wind. Big temperature drops can indicate a strong North wind. A strong head or tail wind can effect your mileage especially at 80 mph.

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My brother has the same problem with his ecoboost. In extreme cold the mileage drops. Ford told him the intercooler being cold causes more air into the intake which the ECU compensates for by adding fuel to the mix. The engine ends up running rich and burning more than it really needs to. 

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My ecoboost definitely runs way better in the heat of the summer. Not that it's any slouch in the winter though, even info do need plugs and coils

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1 hour ago, Scott F said:

What were the winds like during these trips? 70 degrees in the winter often suggests a strong Southerly wind. Big temperature drops can indicate a strong North wind. A strong head or tail wind can effect your mileage especially at 80 mph.

No wind to speak of either day.  I've experienced that often enough out here.  Even a strong crosswind makes a difference in mileage.  

 

2 hours ago, Bass Turd said:

I understand there are winter and summer blends of gasoline. I have no idea what the difference is but I do know people complain about lower MPG with the winter blend. 

I could have attributed it to this if it hadn't been on trips just one week apart in January.

 

1 hour ago, CroakHunter said:

My ecoboost definitely runs way better in the heat of the summer. Not that it's any slouch in the winter though, even info do need plugs and coils

Right this... my F-150 has power to burn.  Amazing what they've done with only 6 cylinders.  

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It's not apples to apples but my work truck is a '17 Colorado that I put at least 150 miles on a day more in the summer and the mileage hasn't changed more than 1 mpg between seasons.

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I spend far more time driving in temps above 40°, so the mileage swing isn't a big concern for me, I was just curious as to the reasons for it.  Now, if I could figure out how to get more than 10 mpg when towing my camping trailer, then I'd really have something. :D

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5 hours ago, Crappiebasser said:

Ford told him the intercooler being cold causes more air into the intake which the ECU compensates for by adding fuel to the mix. The engine ends up running rich and burning more than it really needs to

It's not actually wasting fuel.  It is actually running more efficiently and producing more horsepower.  Cold air is denser and contains more oxygen per the same space.  So your intake will hold "x" volume of air.  If the incoming air is 80 degrees when it fills the intake (x) it contains a certain amount of oxygen.  But if the air occupying "x" is at 10 degrees instead of 80 degrees it now contains significantly more oxygen.  The engines computer absolutely must maintain the proper air/fuel mixture ratio so the only options it has is to shut off air coming in or add more fuel to the mixture.  These numbers are just for examples sake as you aren't getting 10 degree air in your engine but that's a whole different story.  

 

Back in my drag racing days I kept a cooler with bags of ice in my trunk.  Once the engine was hot in the summer heat I would pack ice all around my intake manifold right before my next race.  Colder air=denser air=more oxygen=more horsepower.  Your Ecoboost is a very small engine by typical towing/truck standards and they are getting every drop of power they can out of it while keeping it reliable.  You will likely always see a pronounced drop in MPG when the weather turns cold.  It sucks on the wallet but it's an impressive little engine.  

 

Just to make it more confusing...colder air doesn't necessarily use more fuel, but will always burn the fuel more efficiently.  So when you are getting better gas mileage in the heat of summer your engine is actually much less efficient.  Make sense?  LOL :blink:

Edited by BigAngus752
For the sake of clarity
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You guys that say your trucks run better when hot. Heat and turbos go together like water and oil. My last two cars were turbo cars. One had a front mount intercooler. Unless it was like 90 plus degrees with high humidity. I never noticed to munch of a difference in performance. I now own a Subaru STI that has a top mount intercooler. That sits right on top of the engine. So the intercooler gets a lot of heat soak from the engine. Now that its finally winter. The car has come alive. 

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Ok there are several factors at work here. I work for ryder as a diesel tech and they just sent out a newsletter explaining just this. 

 

1. Engine and trans friction increases in cold temperatures due to cold engine oil and other drive-line fluids. Although synthetic helps

 

2. It takes longer for your engine to reach its operating  temp. Which is when it runs the most effeciently

 

3.Warming up your vehicle lowers fuel economy. For example idling gets 0 miles per gallon.

 

4.Colder air is denser, increasing drag on your vehicle, especially at highway speeds.

 

5.Tire pressure decreases in colder temperatures, increasing rolling resistance. Your tires actually flex and flatten out when they meet the road every revolution, this doesn't happen as efficiently in cold temps

 

6. As stated above winter grades of gasoline can have slightly less energy per gallon than summer blends 

 

7. Battery performance decreases in cold weather, making it harder for your alternator to keep your battery charged. 

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1 hour ago, riverbasser said:

Ok there are several factors at work here. I work for ryder as a diesel tech and they just sent out a newsletter explaining just this. 

 

1. Engine and trans friction increases in cold temperatures due to cold engine oil and other drive-line fluids. Although synthetic helps

 

2. It takes longer for your engine to reach its operating  temp. Which is when it runs the most effeciently

 

3.Warming up your vehicle lowers fuel economy. For example idling gets 0 miles per gallon.

 

4.Colder air is denser, increasing drag on your vehicle, especially at highway speeds.

 

5.Tire pressure decreases in colder temperatures, increasing rolling resistance. Your tires actually flex and flatten out when they meet the road every revolution, this doesn't happen as efficiently in cold temps

 

6. As stated above winter grades of gasoline can have slightly less energy per gallon than summer blends 

 

7. Battery performance decreases in cold weather, making it harder for your alternator to keep your battery charged. 

Great post!!!! 

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What I have found is that there is no magic pill for increasing MPG on any newer vehicle short of a chip or reprogramming.  I look at it from the standpoint that wherever you get gains in 1 area you are going to lose something in another....for example a chip will boost performance but it just may be at the cost of some internal parts or transmission.  Bottom line I live with what the manufacturer set the truck to run at.  I traded my 2004 Silverado 2500HD, 6.0, 4WD, 4.10 rears, that got 10-12mpg empty and 9-10 pulling a heavy 21 foot Ranger for a 2016 High Country Silverado 4WD, 8 speed, 5.3 and get 19-20 empty and 13-15 towing the same Ranger.  Actually the new truck tows just as good if not better than the 3/4 ton I traded it for.  I didn't buy my truck to get good mpg, I bought it to tow.  The increased mpg with the new truck is just a bonus. MPG claims are always a hot topic but I have one friend with a Tundra and while it tows well, he got 7-8mpg on a recent long tow from VA to FL with a 20 foot boat, full gear and 3 guys in the cab.  Ouch......

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Wax your truck more.... improved aerodynamics 🙃

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