View Single Post
Old 12-10-2009, 07:04 PM   #37 (permalink)
aerohead
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 16,228
Thanks: 24,375
Thanked 7,357 Times in 4,757 Posts
- 19

Quote:
Originally Posted by zjrog View Post
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!"
  Reply With Quote