iLikeEggs
Potato!
Today's oils are amazing. I remember when Quaker State used to leave a nice sludge build up. Lol. Customers would come in for valve cover gasket replacements and we would show them the sludge and could pretty much tell what oil they were using and then sell them on Pennzoil. That was prior to everyone going synthetic. Manufacturers have also spelled out to oil motor oil manufacturers that the bar ahd to be raised in ter of oil specs. Nowadays I would say that there isn't really a "bad" off the shelf oil out there. No manufacturer wants to put out a product that is incompatable with any vehicle. Even bulk oil at quickie lube places, does have to meet fairly high standards. Otherwise they would be buying motors left and right.8K miles between oil changes?
Frequency is more important for longevity than the whole dino vs syn debbate. Even if you used 99 cent sore oil but changed it at every 2000 miles you'd be better off than going almost 300% overdue for an oil change. Change your oil often. That is the key. Castrol Hi mileage is great oil and the next best thing to Edge which is their full syn. I advise all of my customers to switch over to hi-mileage when at about 90K miles. The syn in the blend helps the seals not leak.
I change my oil every 2000 miles full Castrol Syn Gold. It costs me nothing and my commute is 5-7 miles one way so I do it way more often than most people could afford.