Most definitely your upstream oxygen sensor plays a LARGE part in your fuel consumption, You should have it checked out or replaced.

That's the sensor I was talking about, right? The one that is before the convertor. The other two sensors (after the catalitic convertor) should be downstream. I HOPE to have a good news after I replace that upstream sensor! Thanks for your reply!

Ecotec auto gas mileage
 

Hey Talero,

The EPA numbers for our 2003 Ecotec automatics were 24/33 (thanks for the correction on this Cliff8928!).

My shot in the dark is that once you get that pre-cat 02 sensor fixed, you should get out of the dismal teens for MPGs. and hopefully at *least* get what I am getting in 70/30 suburban/highway driving- about 21.8.

I did a granny run 2 weeks ago- all highway, minimal traffic, about a 70 MPH average, and got a carefully measured 27 MPG- a record for me.

It does seem everyone has noted the last half of the tank goes faster than the first half due to gas gauge design.

Let us know how it turns out.

I was just recently on a trip and managed 30 MPG on the highway, not being light on the pedal either. The rest of the time i get about 23 MPG. EPA ratings for my car are 26 city, 37 highway.

The '03 Ecotec automatic was officially 24/33 from the EPA

Thanks guys for your comments. If the rating for this engine (automatic transmission) is 24/33, then it should easily give 25 in the average... Strange numbers occurr though. Yesterday I replaced the sensor and in a few days I'll be able to check what the result is. Will post it. You guys take care.

Well I just got My 03 2.2L last week, I took it on a road trip of about 140 miles mostly highway, then back and forth to work and stuff for 130 miles all city stop and go. I filled up tonight with 12 gallons and that averages out to right at 23 mpg with 50/50 highway to city....im not impressed my 92 corvette got an average of 28 through its lifetime until I sold it, and it was probably 60/40 highway to city...

Do we know how many people have auto vs manual? My experience with other cars is that a 4cyl with auto does not do very well. I think cause you have to really punch it to get it to move.

I have a manual, do mostly highway and cruise at 70mph. I consistently average 29 - 31 miles per us gallon. (yes I did all the conversions from metric)

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I'm curious to see if the sensor is going to make a significant difference. Let us know what kind of numbers you get

btw, I've never hit 30's. my mileage ranges from 22-25 of 50/50 city/highway. pure highway driving my highest number is 27.86 mpg

I've only got 27 in my 2.4 on the highway at 65 mph. Around town i get...umm...14-15 usually. In the winter around town its about 10. Sucks bad.