Bad Gas Mileage?

[JDL]

Hi. I have a 2003 Outback 4 cyl. automatic with 16k miles. For the last 2 months the gas mileage has been dropping steadily. It was 22 and has dropped to 16. The driving is around town and hasn't changed. No long warm-ups. The tires are at correct pressure. There are no messages from the OBD.

 

The local Subaru service dept. tells me that the loss of 6mpg is not significant and that if there is no OBD activity, there is nothing they can do about it.

 

Has anyone else had this problem? What is the solution? Thanks in advance.

[sasquatch]

Winter gas? In a lot of areas they change the formulation of the fuel they sell at the pump for different seasons.

[rweddy]

Winter gas? In a lot of areas they change the formulation of the fuel they sell at the pump for different seasons.

Yep same issue here in Colorado. I see about 2mpg loss on winter gas.

[hklaine]

It's interesting that the dealer told you that a 25% decrease in fuel mileage is insignificant. They gave no possible explanations? At +/- 850 miles a week it would certainly be significant to me...

 

Here in New Jersey I have experienced similar symptoms (though not as severe). I have also been chalking it up to the fact that they are now serving oxygenated gas here for the winter.

 

-Heikki

[pulloff]

I would agree with everyone else about the oxygenated winter gas/ethanol (»10% ethanol in NY).

 

Some other factors - If you are doing really short around town driving for short periods the car may not have a chance to get up to optimum operating temperature. Temperature will have a significant influence on [in]complete combustion of fuel. Cold temperatures will also cause more friction due to viscous oil. Lighter weight winter oil may also help with mileage on short duration driving.

 

The effects of the short operating duration, viscous oil, and winter gas may compound for poor mileage.

[99obw]

I was down in northern PA Sunday and filled up the tank in the jeep. I haven't finished the tank yet but the mileage looks better, even considering that most of the miles Sunday and Monday were in 4WD. I wonder if the PA formulation has less ethanol in it than the NY formulation does?

 

The suby goes from ~26 MPG summer to ~24 MPG winter, the jeep from ~20 MPG summer to ~17.5 MPG winter. I think most of this change is from idling, as it's my understanding that NY uses ethanol as an oxygenate year round now.