Effects of head wind on MPG

[tig1]

This morning I drove to Rolla, Mo. to visit my Mom in the Fusion. It's 125 miles. On the way down I had a gusty head wind and my MPG dropped to 29.0. This evening, driving back there was nearly no breeze at all and I got 33.1. Both ways I set the cruz at 70. Amazing what a strong head wind can do for mileage.

 

[TFB1]

Driving 70mph into a 30mph head wind is same aerodynamically as driving 100mph in still air... Requires additional power to overcome the extra drag...

 

[WobblyElvis]

The difference in elevation from start to finish can make a difference as well.

 

[tig1]

Originally Posted By: WobblyElvis
The difference in elevation from start to finish can make a difference as well.


In my case it's a non issue.

 

[bbhero]

Spot on analysis here. I noted a 4 mpg drop into a headwind of 20 mph with gusts to 40. Makes sense because its adds so much drag. In NASCAR at Daytona the headwind down the backstretch really can cut down mpg and mph going into turn 3.

 

[WTJackalope]

West Texas winds can knock 5-6 mpg off of normal mpg. Always wish for a tailwind when traveling.

 

[ammolab]

My CR-V will show a + - 3mpg swing with a strong tail or head wind.

 

[simple_gifts]

Originally Posted By: WTJackalope
West Texas winds can knock 5-6 mpg off of normal mpg. Always wish for a tailwind when traveling.


Which, of course, is a bigger loss than any other state.... j/k.

 

[Michael_P]

We have an instant MPG meter on one of our cars. If you travel down a flat winding country road cruise control set and change your direction from a side wind into a stiff headwind, you can see the MPG instantly go down, sometimes greater than 10%. That is with no downshifting.
I commute by bicycle to work. The days I ride to work in a headwind which is 25 miles one way, I will eat all day long and as much as I can. The days I ride in a tail wind, I eat normally.
It is interesting to see how much more energy is required to achieve the same result in a headwind. Its amazing how much energy you can produce from the wind as well.

 

[CapitalTruck]

Rolla, MO is on Historic 66 right? I recall going through there (I think) when I drove that from MO to AZ

 

[tig1]

Originally Posted By: CapitalTruck
Rolla, MO is on Historic 66 right? I recall going through there (I think) when I drove that from MO to AZ


It is, and several parts of old 66 serve as the otter road to this day. Of course I 44 replaced 66 many years ago. When I was young I traveled that route several times on the dangerous RT 66. This was in the 50s and 60s. I live in Illinois now only three blocks from 66.

 

[wwillson]

Drag increases with the square of flow velocity, so you can see that as you increase the wind speed, the drag increases dramatically.

 

[RedOakRanch]

I crossed the Mojave a few weeks ago with a huge headwind. On what seamed to be flat ground my wife's new Outback 2.5 got a sustained 13mpg instead of its normal 29mpg at 70mpg. It was a scary drive. Usually I wouldn't see more than a 5mpg difference.

 

[The motor guy]

I know my truck can put out an extra 2-3psi of turbo boost cruising at 70 into a headwind.

 

[LubeLuke]

Originally Posted By: TFB1
Driving 70mph into a 30mph head wind is same aerodynamically as driving 100mph in still air... Requires additional power to overcome the extra drag...


While I'm unsure if you would notice a difference, it is definitely not the same aerodynamics as driving at 100mph compared with 70mph and 30mph head wind. This is due to the difference in speed between the vehicle and the road surface. The lower or closer to the road the car is the more difference there will be. Depending on your speed there will be a certain height at which you could disregard the relative ground speed. But this would be reserved for flying vehicles.

 

[robertcope]

Many years ago, when I was new to performance driving, I spent a lot of time at Texas World Speedway; I mean that I was there two or three weekends a month. TWS has a long front straight with big banks that can catch the wind nicely. I remember one weekend when I was several seconds off pace. It made no sense, the car was running great, I was driving great, but the lap times just were not there. Sunday at lunch I happened to sit down next to a semi-pro racer. He was having the same issue. Anyhow, we determined it was the strong headwind slowing us down. I didn't run data at the time, but of course, since then I have and can easily show it to be true.

Another time, when I towed my race car with an '97 Tacoma (supercharged), I was headed home on Sunday into FIERCE winds. Directly into them. I had my foot on the floor, 7psi of boost, and could barely make 60mph. I got about 80 miles on that tank of gas, no joke. It was awful and I vowed never to tow with that setup again...

So, yeah, a few MPG is easily believable with a strong headwind!

 

[tightwad]

Originally Posted By: simple_gifts
Originally Posted By: WTJackalope
West Texas winds can knock 5-6 mpg off of normal mpg. Always wish for a tailwind when traveling.


Which, of course, is a bigger loss than any other state.... j/k.

LOL Yeah, Texans do like to brag, but when it comes to the wind, we're looking for sympathy! I'm 200 miles north of Odessa, in the panhandle. My parents' house is 60 miles northeast of me. The prevailing wind coming down off the Rockies is from the southwest. I get about 28 mpg going and about 24 mpg coming back. On the odd day when the wind isn't blowing hard, it's less of a difference. And you can tell the difference in wind noise and vibration!

 

[Dyusik]

The Hardly and the shoebox (jeep) can attest to the drag. A little gust or change in direction at higher speeds and the speedo plummets.Physics are undeniable.

 

[DoubleWasp]

My Rams feel it even with all the torque motivating them.

My box trucks are downright terrible. But I'd take a headwind over a crosswind any day where those are concerned.

 

[Rick in PA]

Originally Posted By: wwillson
Drag increases with the square of flow velocity, so you can see that as you increase the wind speed, the drag increases dramatically.


And that's just another permutation of E=MV^2
(I do hope our kids are learning basic physics, it touches our lives in so many ways.)