Thanks for the vote SneakyMe.
For brands, anything certified should be sufficient. In
another thread I posted this
PDF link (still works) of a review I have that did actual testing. I save data like that because the experiments approximate real-world conditions, and remind us it's still a science and not magic. In their test, Mobil1 was middling, but I still use it often, as well as RP. Oil weights varied a little, and they didn't test for temperature or inside engines, but they really tried.
I go to small oil-change shops. I've heard horror stories, but I've had no issues. My local dealerships all overcharge, and the small shop employees seem to love it when I watch and help. I should bring oil with me too.
I'm trying to think of anything else I could add. Turbocharged, or in a classic heirloom-type car, I'd be paranoid about oil. Otherwise, as long as the filter takes clumps out and lets oil through, and as long as there's enough oil and its approximately as oily as it originally was, and it's certified and rated to flow at local temperatures, I wouldn't be too concerned.