Before the 1950's the best oil was always a "Pennsylvania-Grade" oil made from Pennsylvania Crude. This was because the oil from that stock consisted of long molecular chains that resisted break-down and therefore delayed wear in engines. It's why Quaker State, Pennzoil, etc etc enjoyed such popularity.
After the big war (WW2) the German ability to synthesize oil from coal, etc. became widely known and refining techniques improved to the point that virtually any ol' grade of crude could be brought up to similar standards as Penn-grade crudes. This revolutionized the motor-oil trade because it was no longer necessary to begin the process with Penn-grade crudes to achieve the high quality.
These days oil is brought into port from UAE, Iraq, Libya, West Texas, and Arkansas and all of it is dumped into the same tanks down at Pasadena, TX etc and refined by SOSUS and placed into whatever plastic bottle various brands wish to order and it's placed on shelves with prices from $2.40 to $8 per quart depending upon whether it's Purple, Blue, or Red bottles.... makes no difference...it ALL meets the ASCME, ILSAC, API, etc etc... the standards necessary to meet EPA, mfr'r warranties, and the industry standardized on a "starburst" symbol to place on packaging so everyone can know the oil in the bottle meets those standards. In fact, the EPA, API, and ILSAC is so picky and demanding that virtually NO DIFFERENCES are allowed because it can defeat the required standards!
The only difference between brands that have that API starburst is PRICE.
I had a '92 Jeep Cherokee that had 330K miles on it when I was rear-ended by a woman driving a Class A motorhome pulling a car-hauler with an Indy-type racecar on it while she was texting. That car used less than a 1/4 qt of oil between 4K mile oil changes and all it ever had in it was WalMarts cheapest SuperTech straight SAE 30 wt oil with that starburst symbol on the package.
I cannot prove that SuperTech cheap oil is why it got to 330K miles without any major repairs.... but I can state without blinking .... that Cheap, SuperTech oil did not PREVENT that car from making 330K miles without any trouble other than batteries, spark plugs, and brakes/tires. Why anyone would spend more than $5 per qt on some exotic brand of oil that is identical to the Starburst SuperTech priced (at the beginning of the experiment) at less than 85-cents/quart is beyond me! But if you want to start an argument just hang around any WalMart and wait for some guy/gal to pick up a quart of Castrol, or Lucas, or Purple Passion or whatever.... and say to them, "you know...that oil your considering is no better than any other on the shelf that has a starburst-symbol on it"... and step back and watch the fisticuffs fly!
Over the years I've had buddies tell me I should switch to some synthetic super-oil they use.... and I just smile and keep the THOUSANDS of DOLLARS I've saved to myself and let them feel confident in their ignorance.
(Putting my NOMEX suit on now for the tirades from people more willing than me to throw money away on overpriced oil. )