I have a '10 Impala that is using oil.
I've only had the oil changed at the dealership and last time I asked them about this I was told the Impalas are known for it.
Does anyone here know Why ?

A gummed up or stuck PCV valve is the first thing I would check out.
Next knowing exactly what weight and oil the dealership is using would be helpful.
Is is still under warranty?
Consider going to a better synthetic oil may really help.

how much, every gm i have ever had lost 1 to 1.5 qts per 5k oil change, new or old

I use to use about 2+ quarts every 5k and that was because my Buick PA liked to leave its signature everywhere it went!
Since I changed the oil pan gasket, I now only loose about 3/4 quart at 5k.
I believe that Gm'* standard for oil loss is what Justin mentioned for acceptable losses.

I've only had the oil changed at the dealership everytime.
I would imagine they would use 5w 30 G.M. oil actually the wife is the one to get the oil changed.
P.C.V. Valve ? I looked at the manual today and didn't see one ?

Is it the 3.5L? It'* probably under the engine cover, on the front valve cover. Should be a vacuum hose coming off it with a "T" at the throttle body

Thanks I will look today.