Why? To pay $2-3 a quart for mineral oil? If you want to run mineral oil, save the money and get Chevron Delo, Pennzoil, or any other good mineral oil for $1.29 a quart. If you only want to spend $3.00 quart for synthetic, get the Shell Rotella Group III Synthetic for $12.98 a gallon at walmart.
Bottom Line, we don't buy oil at the dealer for the same reason that we don't buy tires from the dealer, way to much money for what you get.
When I asked the parts guy some years ago who makes their oil, he said it was made by Pennzoil. This was when Pennspoil was bad.
Now that Pennzoil and QuakerState merged, are they using the same oil?
If so and you want to reward Pennspoil, then you could buy the cheaper of the two.