This has been bothering me for a while i am only getting 22mpg. I do go to a lot of stops, but a lot of times im also going a constant speed of 60. and i try to hyperdrive as well.
I have 20 inch rims on but dont think it should effect it that much
My air filter has already been replaced.
I only have ~40k miles

I know the impala is rated a lot higher or are those just fake ratings, anyone else have some real life ratings they can provide or anything i should look to get checked out first.
Especially guidelines so i dont take it to a repair place and they end up changing everything, to charge me a lot.

even when i reset odomoter and drive in highway it ends up going down to around that much. The only time i got a good mpg was when i first drove it off lot, after i filled it up with gas it just started staying low.
is there a trick to calculating mpg with odomoter better for certain trips without having to reset it everytime since it just keeps averaging everything out

I have been getting around 22-24 MPG in the city and i just got 32 MPG on my vacation last week. I went 426 miles on 3/4 tank of gas. I have 81,000 miles on my 3.4 liter.

By the way welcome to the forum!

Those 20's will cost you mileage, Have you had your car re-tuned for the 20's so that your speedo is correct?

I cant get 27-29 what a joke but 26 on regular

All depends, truly hypermiling (not hyperdriving) takes a lot of practice, years and years and years really.
Not all hypermiling techniques are in fact true savers.
For example cornering at high speed is simply rubbing your fuel mileage "savings" off on your tires.
Taking the long way home to get better fuel economy when in effect it chews up more fuel total...

The best things are a light foot on the throttle, keep your distance from cars in front (stay way back) and stop anticipation (dwb).
You have to learn to let off the gas so far up the road other drivers will constantly chew up your tail and leapfrog you, it's hard to strike a happy balance between fuel economy and the resulting aggravation here.

Are your tires inflated to max.psi sidewall?

Do you carry junk in the trunk or the back seat or on the passenger side?

My car presently sits at 23.7 - 23.8 but I'm rural...
You might even try taking those 60mph runs down to 55...

You want better fuel mileage you're going to have to go all out, v6's aren't made to get but so good...