4G69 Engine Sounds Like a Big Diesel

I have a 4G69 Engine that sounds like a big diesel engine I am looking for ideas on what the damage could be. I'm not sure anything should be done the car gets the same gas mileage and the motor burns a little oil now. I am wondering if it's worth putting in the garage for a couple of weeks and rebuilding the engine myself, or just ride it out. I had a mechanic look at it and give me his guess on what it could be, they said its one of those wait and see things and they didn't know.

Here's what happened to the car,

My Mom has an 09 Gallant with 187k, about 11k miles ago I changed the oil with that 12 month 20k mile Mobile GARBAGE for the first and only time, and went out of town for the winter. Early spring I get a call from my mom telling me the car sounds very loud. I had my brother check the oil, about half of it was missing because it leaked through the front main seal, and the check oil lamp never came on. I had previously replaced the Front main seal when I did the timing belt and water pump 40k miles prior. Now when reguar sythetic oil was added and every oil change since no oil has leaked from the front main seal. It does now burn oil after the event, not at a great amount just where you have to check it after a few thousand miles, It seems to burn less oil in the summer.

Anyone got any ideas on what damage could be causing the excess noise, maybe the maybe bearings almost spun out?
Thanks for any regards,