Subaru losing mpg


#1

I have a 2002 legacy wagon which I bought new. It has always gotten approximately 25 mpg, however the last few months I’m lucky to get 20. The mechanic has found no leaks along the fuel line. The tires are properly inflated, balanced and aligned. The brakes are good. Any suggestions as to what might be causing this drop in mpg? I can barely afford to drive this car any more.


#2

If the spark plugs haven’t been changed recently, change them now. Is the air filter recent? A cleaning of the intake tract with MAF spray cleaner, and carb/throttle body cleaner, could help.


#3

The last few months here in NE means it was winter…and they use the reformulated gas which by itself gives you less performance and worse gas mileage. But that shouldn’t account for 20% drop.

Start with a tune-up if it hasn’t been done in while (especially plugs). Usually with that much of a drop in gas mileage you’ll notice other things like performance… Has it been driving OK???


#4

It’s been driving the same as always - haven’t noticed any change in performance. Will check plugs and filter anyway…thanks.


#5

It turns out there was a bad plug. However that was fixed a month ago and mpg is holding steady at 20 - I’m getting just over 300 miles on a tank. When we first got the car we could get close to 400. Any more ideas? If I wanted 20 mpg I’d get a minivan and at least be more comfortable with my 3 kids…


#6

My best guess is that your thermostat is stuck in the open position, and is allowing the engine to run too cold. This leads to running on a richer gas/air mixture, hence lower gas mileage.

This is just my theory, but it is certainly worth checking out. Since checking the thermostat will involve the same labor as replacing it, I suggest that you just have your mechanic change the thermostat. With any luck, this will help.

The only other things that I can think of are a dragging brake caliper, or a wheel bearing that is going dry. If the thermostat does not prove to be the source of your problem, then you might want to check the other things I mentioned.