Here was my comment in the other thread where you posted this:
You need to check oil every fill-up, making sure that you wait at least 10 minutes after killing the engine before you use the dipstick. These V6 engines have the slowest drain rate into the oil pan of any engines I've ever encountered. If you only wait a minute or two, you WILL get a false reading showing the oil as lower than it really is.
If you were really 4 quarts low 2 weeks after an oil change, then unless they didn't fill it correctly, you'd be seeing blue smoke every time you started the vehicle. I suspect you need to change your technique with the dipstick and give the car more sitting time after you kill the engine before you pull the dipstick.
And this additional comment: don't trust Jiffy Lube or any of its clones. The monkey-lads there are usually novices and they're prone to leaving oil pan plugs loose, installing filters improperly and mis-counting oil quarts.
If you have the oil changed at a quickie-lube place, before you drive any distance, pull over, let it idle and look for leaks in case they didn't get the filter installed correctly. Then kill the engine, wait 10 minutes and check the oil using the dipstick. If that checks out, the only think you have to fear is that they forgot to tighten the oil pan plug. Not much you can do about that without getting under it and using a wrench to confirm it's tight. Then hope they didn't over-tighten it!
I suggest you establish a relationship with an independent shop that knows what they're doing, and have them do your next oil change. You don't need a dealer, but you need a place where you can presume the workers are competent. Quick lube places are NOT in that category.