Bad MPG is freezing weather
Cadillac
 

Cadillac Forums | Help Us Help You | Advertise | Cadillac Parts | Cadillac News | Cadillac Classifieds / (Old System)

Cadillac Technical Archive | Cadillac Dealers | Cadillac Reviews | Cadillac Dealer Reviews | Cadillac Vendors

CadillacForums.com is the premier Cadillac Forum on the internet. Registered Users do not see the above ads.
+ Reply to Thread
Page 1 of 2 1 2 LastLast
Results 1 to 15 of 19
Northstar Engines and System Technical Discussion Discussion, Bad MPG is freezing weather in Cadillac Engine Technical Discussion; I live in Wisconsin and I've noticed that my car gets less than 13mpg in the city and barely 20mpg ...
  1. #1
    weister42 is offline Cadillac Owners Enthusiast
    Automobile(s): 1998 Cadillac Deville Sedan
    Join Date
    Feb 2005
    Posts
    897

    Bad MPG in freezing weather

    I live in Wisconsin and I've noticed that my car gets less than 13mpg in the city and barely 20mpg on the highway when it gets real cold here, but I get much better mpg in the summer times, like 26 on the highway and almost 20mpg in the city. It was the same for the past two years.


    I have no codes besides a P0442 which is small leak in the EVAP system, probably slit the hose under my car from when I ran over a deer carcass two years ago. I replaced the EVAP canister valve and that didn't help clear the code(I clear the code and it comes back in a few days), I can't see any leaks in the engine bay and the screw cap is tight. My Deville has 176k miles but it runs just fine, I can still spin my tires on pavement without much effort. I do have a set of snow tires on which is much softer, but that shouldn't cause the sharp drop in mpg.

  2. Remove Advertisements
    CadillacForums.com
    Advertisements
     

  3. #2
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
    Join Date
    Jun 2004
    Location
    Woodstock Ill.
    Age
    66
    Posts
    74,777

    Re: Bad MPG is freezing weather

    Have you checked for a leaky FPR? That will certainly lower your fuel mileage.

  4. #3
    dkozloski's Avatar
    dkozloski is offline Cadillac Owners 10000+ Posts
    Automobile(s): 2006 STS V8 AWD, '95 Ford Ranger
    Join Date
    Jul 2004
    Location
    Fairbanks, Ak
    Age
    75
    Posts
    26,920

    Re: Bad MPG is freezing weather

    During warmup in the winter the fuel control is in open loop and operates off of mixture tables that are calibrated to deliver a very rich mixture at low temps. After the motor is fully warmed up and coolant temperature is up the fuel control switches to closed loop and everything leans out to normal. Driving short trips in -30F weather I can go through a tank of gas in 150 miles or less.
    Don't mess with Binky Bear!


  5. #4
    weister42 is offline Cadillac Owners Enthusiast
    Automobile(s): 1998 Cadillac Deville Sedan
    Join Date
    Feb 2005
    Posts
    897
    Thread Starter

    Re: Bad MPG is freezing weather

    Quote Originally Posted by Ranger View Post
    Have you checked for a leaky FPR? That will certainly lower your fuel mileage.

    I replaced my FPR about 4 years ago or so, pretty sure it is still good but I'll check to see if any gas is coming out of the nipple.


    I know the fact that gas engines need more fuel to stay running in really cold temperature but I wasn't expecting a drop of 5 or more miles per gallon. Now I know what's like to own an Escalade haha.

  6. #5
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
    Join Date
    Jun 2004
    Location
    Woodstock Ill.
    Age
    66
    Posts
    74,777

    Re: Bad MPG is freezing weather

    The difference between summer and winter should be no more than about 2 MPG. That has been my experience. 5+ seems too high.

  7. #6
    maeng9981's Avatar
    maeng9981 is offline Cadillac Owners Connoisseur
    Automobile(s): 14 SRX, 12 Sierra, 00 SLS, 99 Deville 50-year Anniversary
    Join Date
    Mar 2009
    Location
    Dallas, TX
    Age
    23
    Posts
    3,290

    Re: Bad MPG is freezing weather

    I am experiencing about none or ~1 mpg drop. Texas does not get that cold, so that might be a reason. But 5 mpg seems too excessive for me, though.

  8. #7
    weister42 is offline Cadillac Owners Enthusiast
    Automobile(s): 1998 Cadillac Deville Sedan
    Join Date
    Feb 2005
    Posts
    897
    Thread Starter

    Re: Bad MPG is freezing weather

    Just went for lunch a couple of hours ago and I used about a gallon of gas to warm up the car and drive a few miles to a restaurant and back.


    It is going to be -15 degrees ambient tomorrow. God damn Wisconsin, you're trying to be the North Pole's little brother.


  9. #8
    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
    Automobile(s): 2002.5 F55 STS/65500mi, 2004 Ford F150 SuperCab4x4
    Join Date
    Feb 2006
    Location
    MD Eastern Shore - Kent Island
    Age
    75
    Posts
    45,947

    Re: Bad MPG is freezing weather

    Quote Originally Posted by weister42 View Post
    Just went for lunch a couple of hours ago and I used about a gallon of gas to warm up the car
    There's your mileage problem - let the car sit and warm up and your gas mileage is exactly zero, and that factors heavily into both actual gallons used and the gas mileage DIC average.

    As Cadillac recommends: get in, start the car, adjust your seat belt and drive away normally. Excessive "warmup" times and cold weather idling is death on an engine - the engine warms quicker under moderate driving conditions than sitting at idle, unloaded.

  10. #9
    weister42 is offline Cadillac Owners Enthusiast
    Automobile(s): 1998 Cadillac Deville Sedan
    Join Date
    Feb 2005
    Posts
    897
    Thread Starter

    Re: Bad MPG is freezing weather

    Quote Originally Posted by submariner409 View Post
    There's your mileage problem - let the car sit and warm up and your gas mileage is exactly zero, and that factors heavily into both actual gallons used and the gas mileage DIC average.

    As Cadillac recommends: get in, start the car, adjust your seat belt and drive away normally. Excessive "warmup" times and cold weather idling is death on an engine - the engine warms quicker under moderate driving conditions than sitting at idle, unloaded.

    I donno man, my engine doesn't idle too well when it's below 30 degrees and one of my pulleys makes noise when it's cold, getting that looked at this weekend. Remember this is Wisconsin, we're having -30 degrees for a wind chill tonight.

    I only warm the car up until the coolant temp says 70 degrees so technically it is still "cold", I really doubt you should drive away like normal when the coolant temp is showing negatives. I had an old Ford Taurus that can start in single-digit weather and drive away like it's brand new but not my caddy, ol' roy is getting older and glitch happens.

  11. #10
    dkozloski's Avatar
    dkozloski is offline Cadillac Owners 10000+ Posts
    Automobile(s): 2006 STS V8 AWD, '95 Ford Ranger
    Join Date
    Jul 2004
    Location
    Fairbanks, Ak
    Age
    75
    Posts
    26,920

    Re: Bad MPG is freezing weather

    I just got home from a trip to Sam's club, it was -40F, and that ain't that wind chill BS. The car goes through gas like sh!t through a tin horn. I'm lucky to get 150 miles on a tank of gas.
    Don't mess with Binky Bear!


  12. #11
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
    Join Date
    Jun 2004
    Location
    Woodstock Ill.
    Age
    66
    Posts
    74,777

    Re: Bad MPG is freezing weather

    Remember this is Wisconsin, we're having -30 degrees for a wind chill tonight.
    Wind chills do not affect cars. Your car only feels the ambient temperature.

    Sub is absolutely right. Give it 30 seconds, then go.

  13. #12
    dkozloski's Avatar
    dkozloski is offline Cadillac Owners 10000+ Posts
    Automobile(s): 2006 STS V8 AWD, '95 Ford Ranger
    Join Date
    Jul 2004
    Location
    Fairbanks, Ak
    Age
    75
    Posts
    26,920

    Re: Bad MPG is freezing weather

    According to a GM Powertrain engineer that was part of the design and developement team, the Northstar was designed so that as soon as the engine started at -40F you could go immediately to full throttle and the engine would run smoothly. He didn't say how many times it would do it but he did say it made a lot of bad noises in protest.
    Don't mess with Binky Bear!


  14. #13
    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
    Automobile(s): 2002.5 F55 STS/65500mi, 2004 Ford F150 SuperCab4x4
    Join Date
    Feb 2006
    Location
    MD Eastern Shore - Kent Island
    Age
    75
    Posts
    45,947

    Re: Bad MPG is freezing weather

    I would guess that, particularly in the northern tier of states, there are block heater equipped Northstar cars lying around in junkyards. Installation is not too complicated - they're Calrod elements bolted to the lower sides of the block. Worth a try - look at www.car-part.com . Sure will help your electric bill.....

  15. #14
    weister42 is offline Cadillac Owners Enthusiast
    Automobile(s): 1998 Cadillac Deville Sedan
    Join Date
    Feb 2005
    Posts
    897
    Thread Starter

    Re: Bad MPG in freezing weather

    Quote Originally Posted by dkozloski View Post
    According to a GM Powertrain engineer that was part of the design and developement team, the Northstar was designed so that as soon as the engine started at -40F you could go immediately to full throttle and the engine would run smoothly. He didn't say how many times it would do it but he did say it made a lot of bad noises in protest.

    Yeah GM engineers can do that because if it breaks then oh well, just pull another N* from inventory. If I go and do that and my engine blows up then I'm kind of SOL.

    Oh well, I guess I'll just pay up.

  16. #15
    rhslaura is offline Cadillac Owners Member
    Automobile(s): 1999 STS
    Join Date
    Nov 2009
    Posts
    14

    Re: Bad MPG in freezing weather

    I have a 99 STS that has just recently dropped 6-7 mpg. The temp gauge no longer reads straight up which it always did. It now reads a bit better than half way to straight up after 15 min of 70 mph highway driving. No codes, no head gasket issues, lots of power, heat is OK but maybe a bit less than normal. I think it may be a thermostat stuck open so the car is always running rich. Any thoughts? Thanks.

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.
If you do not want to register, fill this field only and the name will be used as user name for your post.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Bookmarks

Cadillac Posting Rules

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
Read about Lincoln | Buick | Kia Forte Forum
Need products for your Cadillac? Check out your options at the links below:

custom floor mats | Cadillac Chrome and Black Chrome Wheels | window tinting