Losing 2 to 4 mpg with no reduction in performance.

Anyone else.

Most likely due to the winter gasoline formulations used in colder climates. Mine are 2- 3 MPG lower this time of year

if the car is otherwise running fine, no CEL, no other obvious issues, it is most likely caused by the winter blend gas.

Edited January 15, 20188 yr by heartless

Try using ethanol free premium fuel if it is available.  Makes a difference for my subi's

Yeah, cold weather.  Below 40 degrees that @*&% CVT holds the ratio too low, won't upshift.  CVT's are just not programmed correctly.

It is not just the gas.  There is less than 2% difference in BTU value between summer and winter fuel.  2 % is not 2 - 4 MPG.

 

Colder air is denser, so there is more wind resistance = lower MPG.

Cold engines take longer to warm up = lower MPG.

Cold transmissions and wheel bearings have thicker lubricants = lower MPG.

Wet roads have water on them that gets picked up and thrown around.  This takes energy, = lower MPG.

I’d guess it’s circumstantial as well - snow weather driving patterns, etc.

 

You can check brakes. They may be working fine but dragging because pins are corroded. Usually they make noise or have some other symptom but I’ve seen them be asymptomatic before as well.

 

Most likely due to the winter gasoline formulations used in colder climates. Mine are 2- 3 MPG lower this time of year

That, crossed my mind. But it hasn't been this significant in previous years.

Thanks

Thanks ALL.

I’ve seen a couple non/symptomatic subarus jump a few mpg after a brake job though I doubt it’s the case here, it’s not very common.

 

Moving, changing jobs, changing shifts, visiting someone, a hobby, home repair, side business, carrying more dead weight - there’s infinite ways driving habits may have changed requiring different traffic, roads, mountains, speeds, idling, etc which impact mileage.

I generally keep an eye on all highway mileage on trips I’ve done a bunch of times and a tank of gas is userd in one day, then I’m generally not affected by weather, traffic, being late to something, etc. I just drive 55 or 75 the whole time on a similar trip I’ve done many times.

Could be the fuel mix for winter but don't overlook the o2 Sensors!!

O2's, Even if there's No Code?

O2's, Even if there's No Code?

I have known them to become faulty without throwing a code.  Best option? Find out the resistance and check them. You might be able to clean them as well with carb cleaner.  I've done it once with success on my 4Runner.  OR, if it has been a while before they have been changed, I would just do them anyway.  There is only one to the best of my knowledge. Something to think about for sure.  Research loss of mileage and bad 02 sensors.

While you are in there, consider cleaning your IAC ( idle air control) using throttle body cleaner.  Should this become clogged, you will be forcing more fuel in to keep it running properly with the air/fuel mix........you might also have less that smooth idle.  While you are at it, a radiator flush is something to be done.  Always good to do that every 25k miles or so anyway IMO.  ALSO, consider cleaning your MAF sensor located in your air intake if your car has it.  CNC Mass Air Flow cleaner is your ticket to a more balanced fuel/air curve resulting in better gas mileage...........but yeah, I would start with your O2 sensor. 

ya know, after some thought, take a look at your knock sensor.  Seems what I have read these are common sensors to fail and also have the symptom of loss in mileage.  Should be 5v.