Subaru winter gas mileage

I have a 2001 Subaru Outback that gets about 370 miles per tank during the summer, but during winter temps (lows in the teens, highs in the 40s) the mileage drops to less than 250 miles per tank. Two different Subaru “experts” just give me the shoulder shrug. Any ideas to correct or minimize the drastic change?

Change your thermostat. If it’s stuck open, it takes the car forever to heat up to operating temperature.

MPG drops a bit in the winter due to colder temps, owners warming up cars, and especially on short trips since car is not running optimally cold. Your method of measuring is very inaccurate as the fuel guage is not very linear. I would recommend using your trip odometer between fillups and dividing miles travelled by gallons to refill fully. It will give a much better picture.

  1. Adjust your tire pressure. Due to the drop in temperatures, those tires have lost at least 3 psi, which definitely impacts negatively on fuel economy.
  2. Do not warm up the engine. The car is ready to drive within about 15 seconds of start-up. Just be sure to drive very conservatively until the temperature gauge registers normal operating temperature.
  3. Replace the thermostat.
  4. Avoid drive-up windows at the bank, fast food joints, etc.
  5. Verify the viscosity of your motor oil. If it is 10w-30, switch to 5w-30.

I thought this was a pretty good article.

I have been thinking about doing a grille block after noticing how long it takes (digital read out from scan-gauge) to warm up to 190 degrees operating temp.

If your thermostat is working, you should never need to block the grille.

I think the idea is that the engine will reach best/efficient operating temp quicker because cold air is not blowing past it and the radiator.

Also, it is only mildly cool temps and engine temps are around 187 vs 190 degrees in the summer once the engine is fully warmed up and car is in motion.

Temps go up to 190 when I am sitting at a light for a bit then quickly go down once I start moving (again, this is happening now and the ambient temps are still pretty mild)

Thanks! I’ll check that.

Thanks for the tire pressure advice!

Thanks for the referral – I’ll give it a try.

Unless you have a diesel or a bad thermostat, you don’t need to do this.

You didn’t include information about your actual drive.
If you are seeing that much of a change on a 50 mile each way highway commute, then there might be something worth investigating.

If your commute to and from work is under 15 miles, and mostly stop and go driving, your car doesn’t have enough time to get fully warmed up, and switched off of the cold engine programming.

Another killer of fuel mileage is winter fuel blends.
They alone will drop gas mileage considerably for lower distance trip driving.

Take your car out for a long highway drive (100 miles each way) on your next day off, and see if you are getting your normal gas mileage then. If yes, then its just your short commute causing the fuel economy loss.


You probably nailed it. My one-way commute to work is about 7 mi. Although it reaches normal operating temp, it’s probably not long enough.