My check engine light came on and I checked it and these two codes came up. I started with replacing the back oxygen sensor, but the two codes are still on. I usually use Chevron gas. I feel like it burns oil quickly, so oil could be moving past the piton rings. It also seems like there is a lower fuel economy.

 

 

Any advice? What could it be, and where should I start with problem solving? Someone I talked to said it could be the Catalytic Converter, could this be true or likely not?

Did you erase the codes after replacing the sensor?

 

Oil consumption is often due to an old PCV valve. Get a new one from Subaru. Big difference between the real thing and an aftermarket cheapo.

 

How low is your fuel economy? Has it dropped suddenly?

Had to respond to mention of a specific brand of gasoline, Chevron.  What few know is all gasoline grades are basically the same, save for the octane ratings (another topic).  The ascertainable difference is the additive packages - detergents - that each of the company will add quite late in the distribution process.  I am a previous Mobil Oil operations employee spending 12 years in that business. Oil companies frequently trade out their fuels, based on octane, and trade these throughout North America and internationally.  This adds big efficiencies to the system.   Feel free to use the lesser cost station of  your choice, unless you are sold on a particular detergent additive.