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mort81 11-07-2012 11:00 AM

Gas mileage decrease when....
 
My heater is turned on. Seems like my mileage has decrease since I have been running the heater inside my Jeep. I have noticed I went from averaging 20 mpg to low 18's according to the EVIC. I usually turn the a/c off when running the heater unless I really need it on. Some morning I do use remote start but for no longer than a couple of minutes. Anyone else having a similar issue or is this normal?

ajs800 11-07-2012 11:14 AM

Re: Gas mileage decrease when....
 
when did you start noticing this? within the last month?

mort81 11-07-2012 11:28 AM

Yeah. Since I have started using the heater as the weather has become cooler.

canis 11-07-2012 11:32 AM

Re: Gas mileage decrease when....
 
Could be that using the heater coincides with colder weather. Colder weather coincides with winter-blend gasoline that results in lower gas mileage across the board.

77rednecktruck 11-07-2012 11:32 AM

Re: Gas mileage decrease when....
 
auto mode probably runs AC to keep stuff defrosted.

I don't care about gas mileage and have not looked in a long time so I don't know if mine is affected also.

2012 Summit 11-07-2012 11:47 AM

Re: Gas mileage decrease when....
 
I''m with canis on this one (ETHANOL)

ColdCase 11-07-2012 12:41 PM

Re: Gas mileage decrease when....
 
The engine runs richer when cold and during the warm up cycle, and cold weather start ups last longer (the engine takes longer to heat up). Mpg hit is normal, especially if you take short trips with cool down in between.

There is also some effect from winter fuel blends, but most of it is the cold start.

There is also some effect of the tires being softer as the air inside contracts and tire pressure is lost which causes more rolling resistance.

There is also some effect that the oil and grease is thicker at cold temperatures.

Running the heater has little or no effect, its just the conditions where you use the heater are also the conditions that use more fuel.

mort81 11-07-2012 01:22 PM

Thanks for the info guys. I'm just paranoid now after having 2 cylinder heads replaced.

WK2007 11-07-2012 01:46 PM

Re: Gas mileage decrease when....
 
Quote: "Colder weather coincides with winter-blend gasoline that results in lower gas mileage across the board."

Actually, there is generally an effort to lessen the amount of Ethanol in gas consumed through winter months. This is because Ethanol has an unfortunate tendency to attract water. See this video for more info:
How Ethanol Gas Attracts Water from the Air - Demonstration - YouTube

If you want to know more, you can also read this article on the subject:
epa.gov/oms/regs/fuels/rfg/waterphs.pdf

Unfortunately, US refineries utilize MTBE as an additive, although it has been proven that this particular additive is commonly the cause of cancers.

Using the automatic settings on your Jeep heater and cooler allows for the A/C unit to run, which decreases gas mileage as Rednecktruck correctly argued.

It is also true that cold starts have a negative impact on gas mileage. However, depending on the distance travelled when driving your car after a cold start may both cause a minimal or a significant impact on your general consumption of gas. Long trips will outweight this tendency, but short trips may amplify the effect.

Hope this helps!

Muddy4DSM 11-07-2012 01:48 PM

Re: Gas mileage decrease when....
 
Quote:

Originally Posted by mort81 (Post 708166)
Thanks for the info guys. I'm just paranoid now after having 2 cylinder heads replaced.

This the same Mort from Chicago and CLSB?

Doc_d 11-07-2012 01:48 PM

Re: Gas mileage decrease when....
 
It's the winter blend fuels and Chryslers tuning. Every Chrysler vehicle I've ever owned got much worse mileage in the winter. My hemi was averaging 18 - 19 mpg all summer and now I'm down to 16.5 mpg.

mort81 11-07-2012 05:29 PM

Quote:

Originally Posted by Muddy4DSM (Post 708173)
This the same Mort from Chicago and CLSB?

Nope


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