Notices
1999 - 2003 7.3L Power Stroke Diesel  
Sponsored by:
Sponsored by: DP Tuner

Winter MPG Experiment

Thread Tools
 
Search this Thread
 
Old Nov 14, 2013 | 08:09 AM
  #1  
Tugly's Avatar
Tugly
Thread Starter
|
Hotshot
10 Year Member
Photogenic
Photoriffic
Shutterbug
Joined: Jan 2011
Posts: 18,849
Likes: 179
From: Puget Sound
Winter MPG Experiment

It's that time - our fuel is changing. I've had a theory for a while and I'm going to put it to the test:

Did you know that any time you turn the vent select **** to the right that it activates the AC compressor? I could be wrong, but I think that one piece of hardware uses about 5 HP to operate. I read a number one time - stating it takes about 60 HP to keep our trucks at highway speed (60-65 MPH) on the flat with no wind. If I add that 5HP load when I want warm feet, that's close to a 10% hit on my fuel economy. I pulled the plug on my AC compressor to run this test and see what happens.

Caveats: It's best to cycle the compressor on a regular basis to keep it functioning properly, so this will be temporary. The AC also helps to warm the truck quicker and put warmer air in the nose.

If I'm going to do something like this permanently... I'd put a switch on the AC to kill it when desired, and I'd want a grille cover for those really cold days without the AC running.

OK brothers... I'm ready for the arrows to poke holes in my theories here. Bring it!
 
Reply
Old Nov 14, 2013 | 08:57 AM
  #2  
trk98's Avatar
trk98
Senior User
Joined: Feb 2004
Posts: 249
Likes: 1
Ive always noticed my ac conpressor ran on the split level function and thought it was abnormal. I wonder if the selector can be modded so it doesn't cycle the compressor on that setting. I've never wished for split level ac, however I always use it with heat. Good catch though. One point to add, on my 89 and my corvette on days below 30 the compressor wouldn't even run. I wonder if the same holds true on these trucks?
 
Reply
Old Nov 14, 2013 | 09:19 AM
  #3  
trekbasso's Avatar
trekbasso
Fleet Mechanic
15 Year Member
Joined: Dec 2010
Posts: 1,546
Likes: 9
From: Wellington, Co
Keep in mind one of the functions of the compressor running is to dry out the air, hence the defrost/defog effect.
But this is a good experiment, and your the one to do it right Rich.
 
Reply
Old Nov 14, 2013 | 09:20 AM
  #4  
TinyWonder's Avatar
TinyWonder
Postmaster
15 Year Member
Joined: Jun 2010
Posts: 2,928
Likes: 0
From: Oregon City, Oregon
The A/C also helps to dry out the air in the cabin, reducing humidity build up on the windshield.

Not much of a problem in Tugly's neck of the woods. But it's uber important in the Pacific Northwet... I mean Northwest.

(Dang it. Trekbasso beat me to it.)
 
Reply
Old Nov 14, 2013 | 09:36 AM
  #5  
trekbasso's Avatar
trekbasso
Fleet Mechanic
15 Year Member
Joined: Dec 2010
Posts: 1,546
Likes: 9
From: Wellington, Co
Originally Posted by TinyWonder
The A/C also helps to dry out the air in the cabin, reducing humidity build up on the windshield.

Not much of a problem in Tugly's neck of the woods. But it's uber important in the Pacific Northwet... I mean Northwest.

(Dang it. Trekbasso beat me to it.)
I now live in northern Colorado, but being from Houston I am well versed in humidity.
 
Reply
Old Nov 14, 2013 | 09:42 AM
  #6  
SteveH-CO's Avatar
SteveH-CO
Fleet Mechanic
20 Year Member
Liked
Loved
Community Favorite
Joined: Jul 2005
Posts: 1,800
Likes: 52
From: Southern Colorado
All sounds good to me - I dislike the fact that Ford didn't provide a separate A/C switch on the F series. I agree that you should cycle the compressor 1x/mo or so to keep the system oiled internally. As others mentioned, it shouldn' run below 30-ish F, due to icing concerns.
 
Reply
Old Nov 14, 2013 | 09:50 AM
  #7  
RV_Tech's Avatar
RV_Tech
Hotshot
Joined: Jan 2010
Posts: 10,060
Likes: 491
From: Bristol, TN.
So how will you actually track the change? Time frame, miles? Results may be difficult to interpret if variables are completely random, thus a lengthy time frame or a good numbers of miles may be necessary to see reproducible result. Also would you not first need to leave the plug alone and establish a baseline, before disconnecting the plug, unless you have already done so. Just wondering

Steve
 
Reply
Old Nov 14, 2013 | 01:12 PM
  #8  
Shake-N-Bake's Avatar
Shake-N-Bake
Post Fiend
Joined: Sep 2003
Posts: 6,096
Likes: 26
From: Mesa AZ
Club FTE Silver Member

I get better fuel mileage during the summer than during the winter. I think the winter blend has something to do with that. Cleatus says it's likely due to the fact that a lot of us start our truck and let it idle in the driveway while we get ready for our day....that theory makes a lot of sense to me.

Where I live we use the A/C 100% of the time from mid April to mid November. I see zero effect on MPG whether the A/C is used or not. I don't use the A/C at all during the winter since I never use the bi-level setting on my truck. I can't stand warm air hitting my face....
 
Reply
FTE Stories

Ford Trucks for Ford Truck Enthusiasts

story-0

Top 10 Ford Truck Tragedies

 Joe Kucinski
story-1

AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make

 Brett Foote
story-2

Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!

 Michael S. Palmer
story-3

Ford's 2001 Explorer Sportsman Concept Looks For a New Home

 Verdad Gallardo
story-4

10 Best Ford Truck Engines We Miss the Most!

 Joe Kucinski
story-5

2026 Shelby F-150 Off-Road: Better Than a Raptor R?

 Brett Foote
story-6

2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!

 Michael S. Palmer
story-7

10 Most Surprising 2026 Ford Truck Features!

 Joe Kucinski
story-8

Top 10 Ford Trucks Coming to Mecum Indy 2026

 Brett Foote
story-9

5 Best / 5 Worst Ford Truck Wheels of All Time

 Joe Kucinski
Old Nov 14, 2013 | 03:37 PM
  #9  
RV_Tech's Avatar
RV_Tech
Hotshot
Joined: Jan 2010
Posts: 10,060
Likes: 491
From: Bristol, TN.
It will indeed be a difficult theory to test with so many variables. I also never run bi-level for the same reason.

Steve
 
Reply
Old Nov 14, 2013 | 04:13 PM
  #10  
Shake-N-Bake's Avatar
Shake-N-Bake
Post Fiend
Joined: Sep 2003
Posts: 6,096
Likes: 26
From: Mesa AZ
Club FTE Silver Member

Originally Posted by Tugly
...Did you know that any time you turn the vent select **** to the right that it activates the AC compressor? ...
The A/C compressor should not turn on in the FLOOR position. Here are the pages from the service manual that explains the operation for each switch position. I included both 1999 and 2000 since the operation is slightly different between the two years...

 
Attached Images
Reply
Old Nov 14, 2013 | 04:20 PM
  #11  
Tugly's Avatar
Tugly
Thread Starter
|
Hotshot
10 Year Member
Photogenic
Photoriffic
Shutterbug
Joined: Jan 2011
Posts: 18,849
Likes: 179
From: Puget Sound
I've been tracking my mileage and I have a long-haul coming, where I usually have the heat on with winter-blend fuel. It will probably be inconclusive (no real difference), but it doesn't cost anything to try.
 
Reply
Old Nov 14, 2013 | 04:23 PM
  #12  
Shake-N-Bake's Avatar
Shake-N-Bake
Post Fiend
Joined: Sep 2003
Posts: 6,096
Likes: 26
From: Mesa AZ
Club FTE Silver Member

Originally Posted by Tugly
... Anything to the right of "OFF" activates the AC compressor. ....
That is odd. Something may be wrong with your system then....
 
Reply
Old Nov 14, 2013 | 10:20 PM
  #13  
timmyboy76's Avatar
timmyboy76
Lead Driver
Joined: Sep 2010
Posts: 7,793
Likes: 50
completely normal operation in my truck. The bi-level indeed will chill my feet/face, during the summer. Heck, i never switch to A/C or MAX, because the ni setting is cold enough...i wonder if the Ranger Mod had anything to do with this/that?
 
Reply
Old Nov 14, 2013 | 11:09 PM
  #14  
t.scottNDU's Avatar
t.scottNDU
Senior User
Joined: Sep 2013
Posts: 498
Likes: 0
From: Hagerstown, MD
My trucks stays on bi-level all winter long. I hate that hot air hitting my face as well. Although I also hate the dry air from the defroster bouncing off the windshield and hitting my eyes first thing in the morning too.
 
Reply
Old Nov 15, 2013 | 05:04 AM
  #15  
Tugly's Avatar
Tugly
Thread Starter
|
Hotshot
10 Year Member
Photogenic
Photoriffic
Shutterbug
Joined: Jan 2011
Posts: 18,849
Likes: 179
From: Puget Sound
Originally Posted by Shake-N-Bake
That is odd. Something may be wrong with your system then....
You caught me mid-edit. I have not confirmed anything with feet-only, I just know three of the four settings are confirmed.
 
Reply



All times are GMT -5. The time now is 07:56 PM.

story-0
Top 10 Ford Truck Tragedies

Slideshow: Top 10 Ford truck tragedies.

By Joe Kucinski | 2026-05-18 19:34:33


VIEW MORE
story-1
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make

And it might be even better than that.

By Brett Foote | 2026-05-18 19:26:42


VIEW MORE
story-2
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!

Slideshow: Does lowering an F-150 Lobo RUIN the ride quality?

By Michael S. Palmer | 2026-05-18 19:20:37


VIEW MORE
story-3
Ford's 2001 Explorer Sportsman Concept Looks For a New Home

Slideshow: Ford's bizarre fishing-themed Explorer concept has resurfaced after spending decades largely forgotten.

By Verdad Gallardo | 2026-05-12 18:07:46


VIEW MORE
story-4
10 Best Ford Truck Engines We Miss the Most!

Slideshow: The 10 best Ford truck engines we miss the most.

By Joe Kucinski | 2026-05-12 13:09:47


VIEW MORE
story-5
2026 Shelby F-150 Off-Road: Better Than a Raptor R?

Slideshow: first look at the 810 hp 2026 Shelby F-150 Off-Road!

By Brett Foote | 2026-05-12 12:50:07


VIEW MORE
story-6
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!

Slideshow: Everything You Need to Know about the 2027 Super Duty Carhartt Package!

By Michael S. Palmer | 2026-05-07 17:51:06


VIEW MORE
story-7
10 Most Surprising 2026 Ford Truck Features!

Slideshow: 10 most surprising Ford truck options/features in 2026.

By Joe Kucinski | 2026-05-05 11:17:22


VIEW MORE
story-8
Top 10 Ford Trucks Coming to Mecum Indy 2026

Slideshow: Here are the top 10 Fords coming to Mecum Indy 2026.

By Brett Foote | 2026-05-04 13:49:49


VIEW MORE
story-9
5 Best / 5 Worst Ford Truck Wheels of All Time

Slideshow: The 5 best and 5 worst Ford truck wheels of all time

By Joe Kucinski | 2026-04-29 16:49:01


VIEW MORE