Sudden decline in mileage

[jnaught]

My new to me 2001 Forester L consistantly got 24-25 MPG for the first 2 months, now has dropped to 21-22. It does not run noticably rougher and does not to exhibit a power loss though it was never a rocket. What to check ?

[cookie]

that may not be that far off. My 99 Forester usually loses about 1 Mpg here in San Mateo CA in the winter. It is mild here compared to your area. Take two asperin and call me in the spring.

[mtsmiths]

Do they sell "winter fuel" in your area. We get lower mpg in winter when they start the oxigenated gas routine (10% ethanol).

 

Less btu's per gallon, = less miles per gallon.

[shimonmor]

My new to me 2001 Forester L consistantly got 24-25 MPG for the first 2 months, now has dropped to 21-22. It does not run noticably rougher and does not to exhibit a power loss though it was never a rocket. What to check ?

How many miles? Could be an O2 sensor going south (a stab in the dark) amongst other things.

[canajun2eh]

Nothing unusual about that. Everything, including your own body, uses more fuel in the winter.

 

I've seen as much as a 10 mpg drop in extreme cold, but 2-3 is more common.

[Leg93]

Check you tire pressure also. My tires list 44 PSI. If I'm down to 40 I'll lose that much MPG. In the cold weather the pressure falls.

 

I agree with the fact that we tend to lose MPG in the cold weather. A fuel additive can help, but the cost of the additive more than surpasses the MPG savings usually. I have found some for little $$ at the warehouse stores.

[idosubaru]

i live 2 miles from PA and i'm almost certain they do the gasoline switch in the winter.....i think MD does (where i live). this will decrease mileage some.

 

check tire pressure of course. you don't have any extra weight in the car do you? gain some extra pounds at thanksgiving? did you switch jobs or routine...in other words your driving habits?

 

i like doing tune ups all at once:

fuel filter

spark plugs

ignition wires (i have magnecor so they never need replaced)

distributor cap

rotor (forester may not have these items, i don't know specifics of that year/model).

air filter

O2 sensor

all this stuff is cheap and easy to do.

 

pull the stored codes, it's possible the ECU might be seeing some degraded performance somewhere. probably not, but no harm to check.