Mileage per gallon

[gmctruck09]

Need some advice from the experts guys.
01 grand am gt 3400, 149000 miles
Is 20mpg average per tank acceptable? Half city, Half highway per tank
Or can I do something to get more MPG. Sure seems like I should be getting better than that. maybe my expectations are to high.
Thanks in advance.

[3100]

yes that is normal, this are not fuel efficient engines

[goodoldpapa]

I get about 27 MPG. If you haven't changed your front O2 sensor, you will get about a 20% increase in MPG when you do, plus making sure other regular maintenance has been done (spark plugs, spark plug wires, fuel filter, air filter,etc.)

[gmctruck09]

Thanks for the help.
I have not had any codes or service engine light.
Would the O2 sensor still need replaced, without any codes, or se light.
Could it need replaced without any indicators showing up?

[3100]

this is very broad topic two identical cars with same millage same size drivers with same driving habits will have two different mpg results, and not to mention the following:

tire size (wider tire = more rolling resistance)
low tire pressure = more rolling resistance
lazy O2
unnecessary weight in the trunk
drivers driving habits
paved/unpaved road
snow on the road
weather temperature
sea level (you can drive your car on flat surface at 5000 ft above sea level and you will use more gas than someone who drives the same car at 100 ft above sea level) every 1000 ft above sea level you will lose 3% of power.
winter time gasoline evaporates faster (gas stations use different mixtures of gasoline during winter and summer)
different cites have different stop and go traffic
also gas station pumps are not always precise (not calibrated properly) you might think that you are getting ie. 10 gallons but maybe the same gas station is robbing you slowly that you don't notice on our so accurate gm fuel gauges so instead of 10 gallons you maybe get 9.4. and maybe weights and measures guys have certain charts for tolerance so 9.4 could be acceptable in general. So this is just some out of many variables that have impact on our mpg results.