Acura Repair: 04 RSX & Bad Gas Mileage!, wideband o2 sensor, gasoline brands

Question
I have a 2004 RSX Automatic that gets horrible gas mileage. I'm talking about 200 miles per tank mixed city/hwy.

It has 14,000 miles and is bone stock never modified.

I have tried the following:

factory alignment specs twice

new MAF

different gasoline brands and octane ratings from 87 to 91 octane.

checking tire pressures like a mad man.

different drivers to make sure it's not just me.

Automatic mode and Sport shift mode.

new air filter

new spark plugs

I had the dealer check the catalytic converter by doing a "unofficial" smog test, whatever that is and came up with a c02 rating of 14.8 @ 3000rpm which they state is super low. Honestly, I don't know.

Thank you for your help!  

Answer
Hi Darren,

I'm assuming your engine light is not on either. 14.8 is a good o2 reading, the best advice I could give you Darren is to take it to a dyno shop where they will use a wideband o2 sensor. The issue is that your o2 sensor in your car can only read a range around 14 so it will not really give you an accurate reading. The only person that can tell you why your losing so much gas mileage is a dyno tech as he can watch the power band and air and fuel consumption very closely. Dealerships only go by the book so you could spend thousands and still not find the issue.

Let me know how that goes, and if you have anymore questions.

Thank you,
Daniel