I've grown fond of Mobil-1 from my Sprinter days. I don't think there is a much better oil, especially when the boutique oils (Amsoil) have been shown to be not so great by independent testing. Amsoil vendors will strongly disagree, and show you all the stats from the Amsoil labs and tests, I'm sure.
I stopped using Pennzoil in the 80's when my Dad showed me the underneath of a oil filler cap and said "it looks like they used Pennzoil" because there was a brown sludge clinging to the cap. He said that only happened with Pennzoil; to be fair, that was conventional oil and almost 40 years ago.
With prices what they are, I don't know why anyone would go with conventional oil or semi-synthetic. A 5-quart jug of Mobil-1 is only about $25 at Walmart. Saving $5 by going with the cheapest oil is foolish, because you have no idea what you're getting. And $5 over 5-10,000 miles doesn't add up to much per mile!
I've always noticed a change after a fresh oil change, and also after going from conventional oil to synthetic; but that may have been because it was a fresh oil change.
2015 T250 MR cargo w/windows, LS. Purchased new 9/2016. Richmond, CA
Go Ducks! track&field 84-86