Our oll capacity is 4.5 US Qts. You can add up to 5 US Qts without an issue, but I'd bet nearly 6 quarts is getting a bit overfull. Does the oil appear foamy or bubbly on the dipstick?

Another thing to consider is recently most states swapped over to their winter blend fuel and that, along with warming up the car before heading out, or cold start needing more fuel vs air can impact mpg'* as well.

The plugs, unless old and worn shouldn't effect mileage. the air filter is now, again, no effect when new. I'm with Bill, winter blend drops mileage a bit, warming up the car, a bit more, being cold, more fuel is used, yet another drop.

As for the oil, that'* a bit to much. I say drain out a quart. A little over full is OK, but when it'* so full that the standing oil can contact the crank shaft there can be problems. For one it'* drag. The other, as Bill mentioned, foam in the oil. And that can cause big problems by disrupting flow.

ok, ill go drain and see if i have any improvements tomorrow when i get gas, also, my uncle whos worked for chrystler for 30ish years, told me that when he gaps his plugs, he goes a little higher than recommended so they can burn to proper gap, so my plugs i gapped to .063" too much?

Probably won't make a difference, but I've run 160k miles on my Regal at the proper gap and I never had a problem. I've also noticed a significant drop in fuel economy in the winter over what it was before it cooled down. The PCM is tuned to dump lots of fuel on cold starts to warm up the engine. That will have a pretty big effect on fuel economy.

Also, Bosch plugs are crap for 3800'*. Most people I've talked to who have used them have had bad experiences and they promptly return them and get an autolite/acdelco/champion plug. I've used all 3 brands with equally good experiences.

ok, its below freezing and i havent adapted well yet, just let out about 3/4 of a quart i think and the level on the stick seemed better. also,my maf ibelieve is broke which sseidriver97 informed me that it was the cause of my idle issue, could it also be my mpg issue?

yes very very much so lol..
FYI his maf is broken at the tip like they love to do..i put a diffrent one in from the shop and the idle issue smoothed out but then killed the car and wouldnt let it start so i put his old one back in and boom she ran like she did before....anyways bo yes your bad MAF will help with bad mpgs as its not reading correct airflow and not telling the comp accurate amounts of feul it needs

Yep, a bad MAF will absolutely destroy your fuel economy and idling. Seriously, I would have gone there first without asking any other questions about a tuneup.