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Old 12-27-2012, 06:46 AM   #1
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2.5 mpg drop over last couple weeks

Over the last couple weeks my mpg has really dropped off and I cant pinpoint why because Ive made a few changes.

The Constant: 2013 JKU sport, hard top, RR rock rails, 3.21 gears, manual

at this point I was averaging about 19.5mpg -20mpg overall. I drive 90% highway miles.

The Variables:
On December 15th I added new rims and tires, 17" rugged ridge rims and 285/70r17 cooper ATP tires

Used 4wd for the first time

I didn't reset the mpg calculator, and no AEV pro cal to change the tire size. I noticed my mpg calculator on the dash start to drop over time, but not too badly. I rest the MPG a couple times, but with the holidays my driving was different than usual so I didn't know if I could really trust the mpg readings.

On December 21st we got our first snow storm, and my first chance to use 4wd. It handled like a champ, no complaints there. Now that I have had it turned off a bit, and I've been back to my every day driving habits, the best I can seem to manage mpg wise is 17.5mpg.

It just seems like the rolling resistance is crazy, so I was going down a about a 30% decline on the highway, put the Jeep in neutral, and tried coasting down the hill at 65mph, and I was decelerating quite a bit.

Something just seems off to me. any ideas?

Is this really the result of going from a 32.05" tall and 10" wide tore to a 32.7" tall and 11.22" wide tire? the wheels have 4.75" backspacing, there shouldn't be any rubbing.

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Old 12-27-2012, 07:08 AM   #2
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Forgot to also add that I did the first oil change on the 23rd and switched to mobile one full synthetic.

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Old 12-27-2012, 07:19 AM   #3
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Are you solely relying on the dash readout ?
Did you or did you not program for new tire size ?

But yes, of coarse wider tires will hurt Mpgs.
Gas mileage is also worse in the winter months do to winter gas.

My dash readout dropped 2 mpg since November.
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Old 12-27-2012, 07:29 AM   #4
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Are you solely relying on the dash readout ?
yes, but I just started calculating it with a phone app on my last fill up.

Did you or did you not program for new tire size ?
No I have not, I need to order a procal I guess. I didnt think it would be that big of a deal since I wasnt increasing the size that much. I was hoping to find a deal, but $150 seems pretty standard. I have noticed that my speedo is now about 3mph lower than my gps reading, and they used to be right on.

But yes, of coarse wider tires will hurt Mpgs.

I expected a drop from what I had read, just not that much. Seemed people going to 12.5" wide had about a 1.5-2 mpg loss, I thought I'd be more in the 1 mpg loss.

Gas mileage is also worse in the winter months do to winter gas
.
Didn't think about that.
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Old 12-27-2012, 07:38 AM   #5
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what keeper said,,,, winter gas will kill your mpg's,,, im down about 3 mpg in the last 4 weeks.
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Old 12-27-2012, 07:45 AM   #6
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x3 winter gas...we used to have a hybrid in the family fleet and even that took a big hit on winter gas. Probably 3-5mpg. The first winter I thought wtf? Had it for 5 winters and it was consistent.
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Old 12-27-2012, 07:48 AM   #7
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Cool, well, not cool, dam winter gas

but thanks guys. The place that mounted my tires did a disastrous job, and I was worried they screwed something up. It took them neraly 4 hours to mount the tires, and then when they took it down from the alignment the Jeep wouldn't turn left.

But I suppose if there was an issue on one wheel, the Jeep would be pulling to one side
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Old 12-27-2012, 07:53 AM   #8
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A little math for you. If your speedo is off 3mph as you said, at 60mph that is 5%. That means you are traveling roughly 5% more miles than your odometer says. If you were getting 19.5mpg before, adjusting it 5% down for speedometer I accuracy yields 18.5mpg. So, 18.5 on your computer is really 19.5mpg if your speedo is calibrated. Subtract the 1mpg you expected to lose for the wider tires and you are at 17.5mpg, exactly what you are reading.

I'd say you really did lose 1mpg, and you just need to calibrate the speedometer to show that correctly.
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Old 12-27-2012, 08:03 AM   #9
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Quote:
Originally Posted by Snowren24
Cool, well, not cool, dam winter gas

but thanks guys. The place that mounted my tires did a disastrous job, and I was worried they screwed something up. It took them neraly 4 hours to mount the tires, and then when they took it down from the alignment the Jeep wouldn't turn left.

But I suppose if there was an issue on one wheel, the Jeep would be pulling to one side
what did they do ?
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Old 12-27-2012, 08:17 AM   #10
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With the colder weather, are you starting your Jeep and letting it warm up a bit? I was doing that and noticed my mpg dropped significantly (about 2/mpg). These Jeeps drink a lot when idling. Couple that with less efficient winter gas and other driving habit changes in December (short errands are typical), and the loss of mpg starts to make sense.
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Old 12-27-2012, 08:31 AM   #11
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what did they do ?
They said there is a stabilizer shock that runs side to side that extended when they were doing the alignment. It stopped the wheels from turning left.

I do not know the suspension well enough to know what the official name of the part would be, but the tech didn't sound like he knew either.

I was upset when I saw them tear out of the parking lot in it to test everything. I was pissed off and pretty freaked out when they cam rolling back in after going around the block and almost hit the building because they couldn't turn left into the garage.
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Old 12-27-2012, 08:44 AM   #12
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Quote:
Originally Posted by Snowren24

They said there is a stabilizer shock that runs side to side that extended when they were doing the alignment. It stopped the wheels from turning left.

I do not know the suspension well enough to know what the official name of the part would be, but the tech didn't sound like he knew either.

I was upset when I saw them tear out of the parking lot in it to test everything. I was pissed off and pretty freaked out when they cam rolling back in after going around the block and almost hit the building because they couldn't turn left into the garage.
Jeez !!

You are right. It is called the steering stabilizer.... or shock.
Mounts to the axle, then to a clamp on the tie rod.
I don't know why they would loosen the SS clamp to adjust the tie rod

I would not go there again.
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Old 12-27-2012, 08:59 AM   #13
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I think those Coopers are load range "E". You've added a lot of weight.

You've also added height (leverage) and rolling resistance (width).

Winter fuel sucks.

Cold weather alters the fuel/air ratio used by the computer.

Like has already been said...your decrease is normal. You'll get about 1.5 MPGs back when April comes.
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Old 12-27-2012, 09:01 AM   #14
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my mpg has dropped as well. friggin winter gas
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Old 12-27-2012, 09:01 AM   #15
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Quote:
Originally Posted by Hansen
With the colder weather, are you starting your Jeep and letting it warm up a bit? I was doing that and noticed my mpg dropped significantly (about 2/mpg). These Jeeps drink a lot when idling. Couple that with less efficient winter gas and other driving habit changes in December (short errands are typical), and the loss of mpg starts to make sense.
+1 on significant idling gas consumption increase
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Old 12-27-2012, 09:55 AM   #16
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Snowren I drive the same size tire, I get roughly 16mpg on a good day with decent driving habits.
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Old 12-27-2012, 10:06 AM   #17
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Farkin gremlins and their winter gas.
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Old 12-27-2012, 10:09 AM   #18
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Quote:
Originally Posted by SilverSport
Farkin gremlins and their winter gas.
Those dang gremlins.
But I thought they chew on electrical wire not drink gas?
Wait.... My bad. They need something to rinse it down.
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Old 12-27-2012, 11:02 AM   #19
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Quote:
Originally Posted by kjeeper10 View Post
Jeez !!

You are right. It is called the steering stabilizer.... or shock.
Mounts to the axle, then to a clamp on the tie rod.
I don't know why they would loosen the SS clamp to adjust the tie rod

I would not go there again.
I know right, too bad I had bought a lifetime alignment warranty from them
Oh well, they have other shops near by that it is good at too.

Quote:
Originally Posted by citricacid View Post
Snowren I drive the same size tire, I get roughly 16mpg on a good day with decent driving habits.
ouch...I'm assuming you drive a lot of city miles, or you have a different gear ratio?

Quote:
Originally Posted by WXman View Post
I think those Coopers are load range "E". You've added a lot of weight.

You've also added height (leverage) and rolling resistance (width).

Winter fuel sucks.

Cold weather alters the fuel/air ratio used by the computer.

Like has already been said...your decrease is normal. You'll get about 1.5 MPGs back when April comes.
you're right, they are an e load range. as far as weight goes, I think I calculated under 50lbs. I could be wrong though, I looked at so many different tire/wheel combinations. It just doesn't seem like 50lbs should make a difference to me. It was really tough to find a tire that wasnt load e, and I wasn't going to play around with the whole duratrac balancing game.

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Farkin gremlins and their winter gas.
dam gremlins, must be why my dog was barking the last few nights.
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Old 12-27-2012, 11:32 AM   #20
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Tip: don't check your mileage during the winter months.
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Old 12-27-2012, 07:00 PM   #21
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Mine too- on both the Rubi and the 4Runner- you can blame winter gas.
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Old 12-27-2012, 07:30 PM   #22
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Jeez !!

You are right. It is called the steering stabilizer.... or shock.
Mounts to the axle, then to a clamp on the tie rod.
I don't know why they would loosen the SS clamp to adjust the tie rod

I would not go there again.
and then they recommended he upgrade to a heavy duty SS

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Old 12-27-2012, 07:39 PM   #23
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I have never heard of this whole "winter gas" deal. I didn't notice it last year because my Jeep was brand new and I had yet to put on the new shoes. But this year I have noticed over the last few weeks. I was wondering about this today on the way to work but forgot to post. Anybody have more details? It's just the fuel/air ratio?
Thanks
Lew
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Old 12-27-2012, 08:00 PM   #24
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Quote:
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I have never heard of this whole "winter gas" deal. I didn't notice it last year because my Jeep was brand new and I had yet to put on the new shoes. But this year I have noticed over the last few weeks. I was wondering about this today on the way to work but forgot to post. Anybody have more details? It's just the fuel/air ratio?
Thanks
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Additives they put in the fuel I think
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Old 12-27-2012, 10:10 PM   #25
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^ Yep. I think that's it because of freezing and other various issues associated with the cold weather.
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Old 12-27-2012, 10:41 PM   #26
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my mpg has dropped as well. friggin winter gas
Ditto here as well. MPG's are tanking.

I make three short trips per day (5 miles or less), each one is a cold start. So all the cold starts, combined with the extra idle time before each trip (engine still never warms up fully anyway), combined with the "winter gas" you all speak of (never heard of this before)....

Now keep in mind I'm driving like a grandma to at least save some gas. Feathering the gas, shifting at 2000rpm, being passed by scooters, and my dash readout shows....



And this is up from being in the 12's, but I was shifting closer to 2500 so that may explain the increase LOL. So winter gas, eh? Never noticed any drop in winter fuel economy with any of my previously owned vehicles. Jeeps must be sensitive. Another one of those "it's a Jeep" things? They never end
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Old 12-28-2012, 07:53 AM   #27
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I drive about 10 miles each way to work, mostly highway and I'm geared to 3.73.

Also I haven't got my Procal yet either. So it may be a little higher.
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Old 12-28-2012, 08:58 AM   #28
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Other reasons for poor mpg in winter:
Getting Better Gas Mileage In Warm Weather? Here's Why

I also wonder if the EPA estimated MPG on the window sticker take into account the use of ethanol in gas. Ethanol has a lower energy content per gallon than gasoline.

Winter vs Summer Gasoline explained:
Winter vs Summer Gasoline… yes there is a difference « It's just science… and other stuff
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Old 12-28-2012, 10:08 AM   #29
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Those dang gremlins.
But I thought they chew on electrical wire not drink gas?
Wait.... My bad. They need something to rinse it down.

K-

I hear they randomly move wheel weights too
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Old 12-28-2012, 10:10 AM   #30
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K-

I hear they randomly move wheel weights too
Move or snack on ?

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