2010 Subaru Forester - Fuel mileage dropped by 10% or so - Why?

Windsoran
Sun, 04 May 2025 07:33:44 +0000
Maintenance/Repairs

I have a 2010 Subaru Forester with manual transmission and about 70k miles. Until 2 months ago, mixed driving resulted in 27.6 mpg. Abruptly, following refueling, the mileage dropped to 24.5 mpg.

There are no error codes indicated. Correct tire pressure has been verified, all fluids have been topped-up, correct weight of oil, and filter, has been changed, air filter is clean, mass flow sensor has been cleaned and fuel injection fluid has been added twice to the gas tank. The engine runs/idles well and there has not been any loss of power. The initial bottle of fuel injector cleaner resulted in an increased gas mileage to 25.5 mpg. The second bottle of cleaner has not seemed to make any difference.

Any ideas?

27 posts - 10 participants