Very frustrated (winter MPG)

[wagonman76]

19% gain with 18 MPH tailwind, but 17% loss with 18 MPH headwind? Doesn't seem right. Wind resistance increases SQUARED as windspeed increases linearly. The headwind would put you higher on the chart curve than the tailwind would put you lower on the curve.

[FastPlastic]

Originally Posted by rgathright

You should feel good about this though... most of us (brave enough) cannot do that with our Honda's!

Yeah, the main reason I put up with the poor gas mileage of the four wheel drive SUV is being able to get just about anywhere in the snow.

I notice one interesting thing happen when I was parked in perfectly flat 14". When I came back out about an hour or so later, the wind had cleaned the snow out from under my car down to the pavement. I had a clean spot in front, little trails behind the tires and a big scoop behind the car. The back window had about 2" on it, but the rest of the car was clean as a whistle. I really need to get a camera phone, because this was awesome.

[NeilBlanchard]

Hi,

Originally Posted by wagonman76

19% gain with 18 MPH tailwind, but 17% loss with 18 MPH headwind? Doesn't seem right. Wind resistance increases SQUARED as windspeed increases linearly. The headwind would put you higher on the chart curve than the tailwind would put you lower on the curve.

Maybe the vehicle makes a better sail from the back?

[zjrog]

Hey Fast... I truly enjoy using my Jeep for snow busting. Hoping for some deep snow to play in soon. I just hate to clear it from my driveway. Had 8" of the stuff Monday night. And expecting more this weekend.

I'm feeling better about the MPG loss. When I got to work this morning, it was -19 and that was the mean temp, the windchill was -29... Quite a few trucks didn't start, but then most of us found reasons NOT to head out till it warmed some. Not me... It was COLD!!!!

[bestclimb]

Must be nice being able to wait till it warms up. Ain't no fun driving with 4 tires that are "frozen" into an out of round shape, clunk clunk clunk down the road. Some folks don't shut their cars off over night because they will not start in the morning, though if you do that too much without really blowing it out the H2O in your exhaust can condensate on the inside of your pipes and plug them.

[zjrog]

WOuld seem to me you would be much better served with block heaters. Nope, I had to head out as soon as I got in yesterday morning. I was 15 miles down the road before my tires felt round...

It was only -13 this morning. Someoen elses turn to head out!!

[aerohead]

Originally Posted by zjrog

Hey Fast... I truly enjoy using my Jeep for snow busting. Hoping for some deep snow to play in soon. I just hate to clear it from my driveway. Had 8" of the stuff Monday night. And expecting more this weekend.

I'm feeling better about the MPG loss. When I got to work this morning, it was -19 and that was the mean temp, the windchill was -29... Quite a few trucks didn't start, but then most of us found reasons NOT to head out till it warmed some. Not me... It was COLD!!!!

zjrog,
I was noodling air density numbers around this morning(too damned cold to work outside).I calculated them down to +20-degrees F ( looks like I need to go back and figure some at even lower temps! way lower!!!!!!!!!)

Anyway,at 20-degrees F,compared to SAE's standard 60-degrees,on a day with standard barometric pressure,the air density would be over 8% higher,and your drag would consequently be 8% higher.
If your Jeep's Cd was 0.4,with the colder air,it would be like 0.43.
At your colder temps,it's even worse.
Factor in that your tires are "cold" at 70-degrees F,and that even after 22-miles of continuous driving,when you reach your warmed-up equilibrium temp for all lubes and coolant,those temps are still less than during warmer weather.
Thick oil,tranny fluid,gear oil,coolant,hard tire rubber,and denser air,all conspiring to kick your butt at the gas pump.
" whip me ,beat me,hurt me good!"

[dwtaylorpdx]

With no other change, my Jeep loses 4 MPG going from standard fuel, to E10. Summer or winter. (We have specific pumps out here for "farm" applications.)

My 2.5L Wrangler gets about the same mileage no matter what the temp, (IE sucks)
about 17 mpg combined driving. But will stretch out to low 20's on flat freeway cruise.
Due to the add on off road accessories my engine runs warmer most of the time.

Just anecdotal data to toss on the fire...

Dave

[aerohead]

I put a table/graph together and posted it at the Aerodynamics Forum under a thread of the above title.Hope it helps explain why our mpg can suffer so much in winter.

[Burnt]

I agree; i've been seeing some terrible mileages - especially in the morning when I'm driving to work and my block isn't warm enough........i may throw in an electric block warmer.....