Yep right now I'm using about 6 or 7 year old Valvoline Synthetic got about 2900 miles on it and gee I can't tell the difference????????I've never seen or heard any problems due to oil being old, as long as it is stored in reasonable conditions with a tight lid and the oil meets the spec required for the motor. Pennzoil has been documented (photos) to have some additives precipitate and settle to the bottom of the bottle. Looks like dark sandy stuff but I've never seen it in person. I've had a bottle of PUP 5w30 in the garage for about a year but I shake it up every couple months along with my stash of gear oils and other fluids. So when someone talks about precipitation of additives, I always say shake it up and pour it in, the engine will cook it and mix it together just fine.