My MPG's dropped off a cliff

Jkust

Original poster
Member
Dec 4, 2011
946
So I think i'm running into the first real issue with my 9-7x with 4AWD and the 5.3. Since it started getting colder her in MN the manually calculated MPG's have been dropping. Since I bought the car the average MPG for my identical drive have been about 17.9mpg per tank. The last two fill ups I'm now down to 15.1mpg for the same exact drive. I reset the DIC every fill up and it generally is hovering around 14.9 to 15.1 which are number's i've never seen before these last couple fillups which match the manual calculation. The car runs as it should with no issues or dash lights at all. Anybody have any thoughts on what could suddenly cause a 15% drop in mileage? I will also mention I keep all the tires inflated at 32psi as the 9-7 requires as I always have. Basically nothing has changed except the MPG's. The only thing I can possibly come up with is if the AWD is staying engaged all the time.
 

blazinlow89

Member
Jan 25, 2012
2,088
Winter blend fuel maybe. I watch my gas mileage drop every winter, this winter was a it bad since I put the bigger tires on the truck. Manual calculations are at 12.9-14. Usually around 15.9-17 mpg.
 

Jkust

Original poster
Member
Dec 4, 2011
946
blazinlow89 said:
Winter blend fuel maybe. I watch my gas mileage drop every winter, this winter was a it bad since I put the bigger tires on the truck. Manual calculations are at 12.9-14. Usually around 15.9-17 mpg.

Thanks thats a good point. It's like someone flipped a switch all the sudden. I don't recall this issue last winter which is another reason I am scratching my head.
 

Wooluf1952

Member
Nov 20, 2011
2,663
Milwaukee, Wisconsin
Didn't you recently get a lot of heavy snow? That will really play havoc with the MPG's.
 

deepblue

Member
Dec 5, 2011
56
I'm seeing the same thing with the cooler weather now but I do mostly local stop/go driving. I'll be doing some highway driving next week and see how that goes.
 

am-radio

Member
Apr 24, 2012
178
I drop in fuel economy in the winter. Softer tires and more idling. Right now 17-19 liters per 100km in the city. In summer in the city, about 15 liters per 100km.
 

Denali n DOO

Member
May 22, 2012
5,596
am-radio said:
I drop in fuel economy in the winter. Softer tires and more idling. Right now 17-19 liters per 100km in the city. In summer in the city, about 15 liters per 100km.

Great point, I never even thought of that.
 

Jkust

Original poster
Member
Dec 4, 2011
946
Wooluf1952 said:
Didn't you recently get a lot of heavy snow? That will really play havoc with the MPG's.


Yea we got a foot or so of snow but the drop off in mileage started as soon as the cold temps started in...really a month or so ago and the mpg's have continued to drop. So as a test if I reset the Dic in the morning in the summer on my 20+ mile drive to work I will arrive with generally 18mpgs on the guage...now with the same drive, same speeds, same amount of stop and go, I will arive with 15mpgs on the DIC. If this is a winter fuel issue that will be a bummer.

deepblue said:
I'm seeing the same thing with the cooler weather now but I do mostly local stop/go driving. I'll be doing some highway driving next week and see how that goes.


I'm about 90% highway driving and 10% city to get to the highway. I'd be interested in your results.
 

buttons252

Member
Dec 17, 2012
10
I would assume winter blend would improve gas mileage, dont they reduce the ethanol to reduce cold start issues? I believe they do at least in E85.

Anyway, if your AWD was stuck on that would increase parasitic loss -- but it would be really obvious anytime you were in a parking lot trying to make low speed sharp turns. Expect your front wheels to bind or (crow hop)

Other factors are remote car starters (starting the car before driving to warm it up) more cautious / slower drivers affecting your cruise speed.

FYI my AWD is locked on at the moment and i averaged 18.2 mpg from chicago to grand rapids with cruise set to 71mph. now that im driving around the city im at 15.2mpg i think.
 

Wooluf1952

Member
Nov 20, 2011
2,663
Milwaukee, Wisconsin
buttons252 said:
I would assume winter blend would improve gas mileage, dont they reduce the ethanol to reduce cold start issues? I believe they do at least in E85.

Anyway, if your AWD was stuck on that would increase parasitic loss -- but it would be really obvious anytime you were in a parking lot trying to make low speed sharp turns. Expect your front wheels to bind or (crow hop)

Other factors are remote car starters (starting the car before driving to warm it up) more cautious / slower drivers affecting your cruise speed.

FYI my AWD is locked on at the moment and i averaged 18.2 mpg from chicago to grand rapids with cruise set to 71mph. now that im driving around the city im at 15.2mpg i think.


AWD should not bind/crow hop.
 

C-ya

Member
Aug 24, 2012
1,098
Here in SW MI, my mileage drops off every winter. I never paid attention until the last couple of years. My '98 C1500 with a 4.3 usually got 18 mpg, but in the winter it dropped to 12-13. Not looking forward to what the Tb does!
 

buttons252

Member
Dec 17, 2012
10
Wooluf1952 said:
AWD should not bind/crow hop.

Your assuming my AWD was working properly. Just last night, i pulled the encoder motor off and turned the shaft to neutral. it no longer binds now.
 

Jkust

Original poster
Member
Dec 4, 2011
946
buttons252 said:
I would assume winter blend would improve gas mileage, dont they reduce the ethanol to reduce cold start issues? I believe they do at least in E85.

Anyway, if your AWD was stuck on that would increase parasitic loss -- but it would be really obvious anytime you were in a parking lot trying to make low speed sharp turns. Expect your front wheels to bind or (crow hop)

Other factors are remote car starters (starting the car before driving to warm it up) more cautious / slower drivers affecting your cruise speed.

FYI my AWD is locked on at the moment and i averaged 18.2 mpg from chicago to grand rapids with cruise set to 71mph. now that im driving around the city im at 15.2mpg i think.

To my knowledge the ethanol never goes below 10% here in MN where we of course pushed it into existance in the first place before other states against the will of the people. The only time my wheels have crowhopped was the day after it snowed heavily last week and I got to my indoor parking ramp where I need to take a hairpin turn to go downstairs and the wheels crowhopped doing the hairpin turn on wet concrete where it has never happened before. I've never experienced the crowhopping other than that time and I take that same turn twice a day and of course take other sharp turns as well without issue.
I don't warm up my car in the morning and again my parking at work is climate controlled to about 60 degrees in the winter here in MN.
 

Wooluf1952

Member
Nov 20, 2011
2,663
Milwaukee, Wisconsin
buttons252 said:
Your assuming my AWD was working properly. Just last night, i pulled the encoder motor off and turned the shaft to neutral. it no longer binds now.

That's why I said "should not bind/crow hop", not "will not bind/crow hop". :thumbsup:
 

Sparky

Member
Dec 4, 2011
12,927
buttons252 said:
I would assume winter blend would improve gas mileage, dont they reduce the ethanol to reduce cold start issues? I believe they do at least in E85.

Never has for me or anyone else I know around here. Can always tell when it hits. MPG just suddenly drops. Then drops slightly more when it gets even colder and snowier as we idle more while scraping windows etc. Then around springtime the mpg jumps back up again.

That said, my mpg dropped on the TB recently like I expected, but my last two tanks are back up in a normal range, so idk :crazy:
 

Jkust

Original poster
Member
Dec 4, 2011
946
I've been asking around about this and I shouldn't feel too bad. One of my friends has a Prius and he loses 10mpg in the winter down to 38mpg from 48. He's owned it for almost 5 years since new here in MN. Not exactly apples to apples and not quite losing the MPGs for the same reasons either.
 

Jkust

Original poster
Member
Dec 4, 2011
946
So a quick update on this...as you can see in my sig my wife has the identically equipped Rainier to my 9-7 In every way including the 3.73 and 5.3. Well I suppose the Rainier tires and rims are different. I've been off work since the friday before Christmas and so have put a lot of highway miles on her truck. She normally puts a mile or two on a day so she couldn't verify previously. She is getting the same mileage as the 9-7...right around 15.0mpg. So it seems the winter blend fuel in addition to the cold temps are the culprit. It really is a big drop I think.
 

deepblue

Member
Dec 5, 2011
56
Just got back from a NY to VA round trip (900+ miles). I averaged about 75mph and got 18mpg with a well loaded vehicle. In the summer, with slightly slower speeds I got 20+.
I think the winter gas has an impact, just a gut feel.
 

Jkust

Original poster
Member
Dec 4, 2011
946
Well since I was off work for a week and a half and did a lot more city driving, I just filled my tank and calculated my mileage. I got 13.1mpg out of the tank probably consisting of 20 miles of city and the balance highway. It's been near or below zero F lately. I can only imagine what 6.0 would be achieving with these conditions.
 

DFWWIZ

Member
Dec 5, 2011
516
Winter blend gasoline is always a different configuration from summer blend. Not to mention cold air is denser than warm/hot so maybe your ecm/MAF/air temp sensors/Cats/O2 sensors are not getting as hot etc and are not able to make the right changes in the fuel trims like it does in summer time.
 

blazinlow89

Member
Jan 25, 2012
2,088
I am down to about 12.9. Getting about 235 miles to a tank before the light goes on. Really sucks. Does not help I went to the 245/75-16 tires right before it got cold. Cannot remember what I usually atm.
 

DARKASS04EXT

Member
Nov 21, 2011
193
ive got an EXT w/ 3.42, 4x4, on 265/40/22s and my mpg is down to 12.1-12.4 was between 15-16mpg then BAM im in the 12s (not the good 1/4 mile 12s either):rotfl:
 

Jkust

Original poster
Member
Dec 4, 2011
946
Funny thing is somehow I always hope the Average Mileage calculator on the DIC isn't correct but it's always right on the money.
 

C-ya

Member
Aug 24, 2012
1,098
I see this and wonder what is wrong with my truck.

deepblue said:
Just got back from a NY to VA round trip (900+ miles). I averaged about 75mph and got 18mpg with a well loaded vehicle. In the summer, with slightly slower speeds I got 20+.
I think the winter gas has an impact, just a gut feel.

Then I see this:

Jkust said:
Well since I was off work for a week and a half and did a lot more city driving, I just filled my tank and calculated my mileage. I got 13.1mpg out of the tank probably consisting of 20 miles of city and the balance highway. It's been near or below zero F lately. I can only imagine what 6.0 would be achieving with these conditions.

and I think OK, I'm not the only one.

So, do we both have something wrong? Or have our vehicles aged less gracefully? :crazy:
 

meerschm

Member
Aug 26, 2012
1,079
C-ya said:
I see this and wonder what is wrong with my truck.



Then I see this:



and I think OK, I'm not the only one.

So, do we both have something wrong? Or have our vehicles aged less gracefully? :crazy:

You have a longer (heavier) TB
 

C-ya

Member
Aug 24, 2012
1,098
meerschm said:
You have a longer (heavier) TB

So what is wrong with Jkust's Saab?
 

Jkust

Original poster
Member
Dec 4, 2011
946
C-ya said:
So what is wrong with Jkust's Saab?

So if it is supposed to get 15 mpg per the bogus EPA sticker in the city and I get 13.1 and I think 18 or 19 sticker on the highway and I get 15.1mpg, it seems consistent at least. Now that 13.1 is generous because that was still mostly highway driving. This next tank will tell since I'm back to my normal commute. Also don't forget the SAAB and Rainier are A4wd not true rear wheel drive like the TB's and Envoy's when not locked in. Regardless when you are already sub 20mpg, any drop especially if due to winter fuel blends that are politically motivated is a bummer. If I didn't have the Rainier to compare to, I'd still be suspicious but the Rainier has under 60k miles and the 9-7 just hit 70k miles and they are up to par maintaincewise.
 

meerschm

Member
Aug 26, 2012
1,079
Gee, the EPA estimates are for comparison, not a guarantee....


(but my VW TDI has an EPA estimate of 40 highway and I can get 45 pretty easy if I drive nice and stay on the road and out of traffic. but gives more like 30 in traffic or 35-37 on the road if my right foot is heavy and it is very cold.)


I agree the $$ is an impact and the difference of 5 MPG is a lot more % between 15 and 20 MPG than between 35 and 40.

I get around 15-16 around town, and shy of 20 on the road. ( I could probably get just over 20 but am too impatient:wink:)
 

Jkust

Original poster
Member
Dec 4, 2011
946
meerschm said:
Gee, the EPA estimates are for comparison, not a guarantee....

For sure and which year was it when they finally changed the testing procedure to be more realistic? I feel like it was after 07 but I could very well be wrong. End of the day I'm not complaining about the $ difference or I wouldn't be able to show my face for owning two of these things...more a little dumbfounded at the sheer drop off from summer mileage. I can only imagine when they jam 15% ethanol down our throats as is being discussed up from the current 10%.
 

C-ya

Member
Aug 24, 2012
1,098
Jkust said:
Also don't forget the SAAB and Rainier are A4wd not true rear wheel drive like the TB's and Envoy's when not locked in.

OK, that makes sense then. Thanks.
 

meerschm

Member
Aug 26, 2012
1,079
Jkust said:
For sure and which year was it when they finally changed the testing procedure to be more realistic? I feel like it was after 07 but I could very well be wrong. End of the day I'm not complaining about the $ difference or I wouldn't be able to show my face for owning two of these things...more a little dumbfounded at the sheer drop off from summer mileage. I can only imagine when they jam 15% ethanol down our throats as is being discussed up from the current 10%.

The sure way to find out is to drive through this winter, take accurate records, checking tire inflation readings on a regular basis, and post your amazing increase in MPG in the spring:smile:
 

lairdt

Member
Dec 12, 2012
15
blazinlow89 said:
I am down to about 12.9. Getting about 235 miles to a tank before the light goes on. Really sucks. Does not help I went to the 245/75-16 tires right before it got cold. Cannot remember what I usually atm.

My TB is in getting it's transmission replaced, but even with transmission issues I was getting 15 city and 18 on the highway, bone stock. I hope to do better in the future, not by much, but anything I can get. :smile: Oregon's gas is 10% blend year round so the only real difference is air temp and amount of time at idle due to snow/ice defrosting in the morning.
 

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