Wind Cost Me 3 Miles per Gallon

[hunterridgefarm]

I had to do some Interstate travel yesterday in the F250 Powerstroke. My miles per gallon had been around 14 on the country roads so I wanted to check it on the Interstate.

I filled it up, reset the miles per gallon reading and hit the road. I usually get 19-20 miles per gallon on the interstate and sure enough 20 miles down the road I was at 20.5 miles per gallon.

Yesterday was very windy with sustained winds of 25-30 mph and gust to 50 mph.

So as we headed back home I told my wife I was going to try and hit 21-22 mpg.

Driving back home I was driving into the wind the whole way. Had to stay on the accelerator even when going down hill.

Ended up at 17.5 mpg driving into the wind. So the unofficial scientific study is completed...wind can cost you 3 miles to the gallon !

 

[dgl24087]

You had mild winds, lol. In Roanoke, VA we had gusts to 69 mph, Hot Springs recorded 74 mph gusts. Sustained winds were in the 45-50 mph range. The good news was the combination of high winds and brush fires cancelled the appearances of Hillary and Obama. The bad news is that about 1000 acres (at last report) are burned. I-81 north of Roanoke was closed for a while due to poor visibility from smoke, and several residents had to be evacuated from their homes due to the fires getting out of control. About 80,000 people have lost their power, and many will be without power until tuesday or Wednesday. Numerous others, including myself, had wind damage to their homes. Mine is very minor, will only take a couple of hours to fix.

 

[Wesdor]

We drove to Chicago on Saturday and have a computer in the car that shows mpg. On the way in we were getting 26 mpg for most of the trip.

On the way back it was more like 14 mpg

That is with a Chrysler Mini-Van.

I knew we would be in trouble on the way home unless the wind died down - it didn't. At least the mileage averaged out.

 

[MossRoad]

Two summers ago we drove our Impala out to Montana and back. We averaged 29MPG for the entire 4000 mile trip. We did notice on the way home across most of the state of S.D. a very, very strong headwind for about 8 hours that dropped out mileage down to 18. That's about 30% less mileage. Went through a lot of gas that day.

 

[dgl24087]

Fire update: Total burned so far by 4 fires in in surrounding Roanoke is 4800 acres.

 

[RonMar]

Aerodynamic drag is the square of the airspeed, so doubling the airspeed quadruples the drag on a given structure moving thru the air. It is a big factor, most vehicles use 40% of the energy consumed just to move air out of the way. This figure of course goes up with speed increases...

 

[Zick]

Find yourself a well paced semi to get behind.

 

[Mickey_Fx]

No surprises in wind has big impact on fuel milage. In the formula to calc power needed to move down the road, speed i.e. mostly wind resistance, is a cube function. Double speed and needed power is 8X. Weight, rolling resistance mech losses are small compared to parting the air.

Example, a typ 3500# auto on level grade and 30 mph, power needed 3.2 hp.

Change the weight by 1000# either direction only changes the power needed by ~.5hp.

On the otherhand face a 20 mph headwind and power increases to 8.9 and if 40 mph headwind, power needed is 21.4.

Wind, air resistance, is not your friend unless it is a tail wind.

 

[Bird]

My Saturday experience was just the opposite. I made a 430 mile round trip to a retirement party for a young fellow who's probably going to be my son-in-law before long. He just retired after 20 years active service in the Navy, including a couple of trips to Iraq. And winds in my part of Texas were very light or non-existent so my old Ford Windstar got 25.084 mpg. It's over all average since I've owned it is 19.769.