Mobil1 15w50. $26 for a 5.1 qt jug at Walmart.
Usually Penzoil is the most available 20w50. This weight is getting less and less common as newer cars since the 90's almost exclusively reccomend 5w30. I run Quaker, Mobil, penzoil, ...whatever I find first. Dino, synthetic, it's all the same. Oil is oil. The addatives are what make an oil good or bad. I won't use the plain lable "motor oil" brands, and twice a year I run some ATF before an oil change to clean out any sludge or deposits.
For my newer cars I run 5w 30 Mobil1 synthetic because it rates well with detergents, but try finding it in 20w50. It almost doesn't exist. I think I've come across it twice. Nobody wants to carry it because nobody runs that weight except some motorcyclists and MK1 VW enthusiests.
Castrol 20w50, Wix or (NAPAGold) Filters.
Both cars have External temp controlled Oil Coolers.
Years ago, I learned a hard lesson about oils. Using Wagner off the shelf brake fluid ruined all the seals in my rebuilt 58 Bug-eye Sprite. I have been using Castrol fluids ever since, save for my 81 Rabbit Diesel that I ran 10w30 Pennzoil as it was available everywhere....
Grounds, Grounds, Grounds Replace them things.
Divorces, Great Coffee, and Electrics, all start with GOOD Grounds.
Where are my grounds ?
Castrol High Mileage 20W50 found at any local auto parts store... Wal-Mart in my area does not sell 20W50 in any form.