TERRIBLE FUEL ECONOMY

[FinnB12]

Hi there, I'm the owner of a 2009 subaru impreza 1.5L in New Zealand. Im currently getting 12L per 100km (19.6mpg) which is absoloutely horrendous. So far ive checked o2 sensors, changed air filter, cleaned MAF sensor, checked tyre pressure and had a mechanic check the ECU. The car only has 125,000kms on it (77k miles), and im honestly completely lost. Ive been reccomended to change spark plugs by my cousin whose a mechanic, but he doesnt know anything else it would be, and im not sure spark plugs would cause such a drastic difference in fuel economy. Any help is appreciated.

 

[alberto]

impreza 2010 2.5i automatic

1. City 15L/100kms horrible
2. Highway 8.8L/100kms acceptable

Not sure what I can do to improve city driving!!!

 

[pfarmer]

Hi there, I'm the owner of a 2009 subaru impreza 1.5L in New Zealand. Im currently getting 12L per 100km (19.6mpg) which is absoloutely horrendous. So far ive checked o2 sensors, changed air filter, cleaned MAF sensor, checked tyre pressure and had a mechanic check the ECU. The car only has 125,000kms on it (77k miles), and im honestly completely lost. Ive been reccomended to change spark plugs by my cousin whose a mechanic, but he doesnt know anything else it would be, and im not sure spark plugs would cause such a drastic difference in fuel economy. Any help is appreciated.

Had a similar issue with a 2015 Impreza and the thermostat was stuck open in cold weather. Connect OBD2 reader and view operating coolant temperature with heater fully on and turned to hot.

 

[alberto]

Can thermostat stuck open affect my impreza 2.5i, also?

I just started in Oct 2023 driving the car daily all city very small trips 5-10kms.
I can understand 12L/100KMs, but 15L/100KMs is on the high side.
My driving style is very conservative.

 

[cshbz]

Just joined to bump this question as well. 2010 Impreza 2.5i automatic hatch (111k km) getting 13-14L/100KM short city. Not extremely cold here, only dropping below freezing once or twice a month. So far only changed the engine and cabin air filters, but interested in other areas to investigate.
Any help would be greatly appreciated! Thanks