Is your oil 3 gallons over full by any chance? It had to go somewhere, I would take it (maybe even tow it) to be pressure tested and checked for intermix.
I wouldn't write this off as a fluke on account of the previous owner. I would much more suspect someone passing off a problem car onto an unsuspecting buyer.
Well, I'm doing an oil change today so we'll see if an idiot previously worked on the car(likely), the car is burning a bit(common), if it it's in the oil (unlikely at this point)