Back in the day, Sales Reps would get new cars, not uncommon to put 50K to 70K a year on one. So Sales Reps got new Buicks, Chevy's, Fords...model determination was more of trunk size bit.
So The Camry came out and the lines "changed", as did a lot of matters in regard to sales reps.
At 300K miles a few guys kept the car and let kids needing HS/ College cars use them. Most of us grew up with Castrol, and many of us just flat dislike anything Esso...Mobil was okay back in the day, when merged Mobil got the axe.
One Camry went 900k miles until - of all things - a dump truck rolled not only into, but "onto" while parked. All this Camry ever used was 5w-30 GTX every 4K miles while "on the road" then 3K or 3 months as a College Car.
My Olds went 190K with GTX , 5w-30 then at 150K went to 10w-30. I sold it, car went 350K total until ...worth more as parts, than getting fixed from getting hit. Engine went to inboard boat set up, trannie for a rebuild on a Truck.
Old man "Doc" a sales rep, said when he got 400k miles on a Olds, he would get himself a Benz. He was a Castrol fan too. His Daughter's car was a Camry he bought with 200k miles...his daughter liked to change her own oil so he bought her cases of GTX 5w-30 and a case of filters to "start the kid out right".
Doc's goal was to put a million miles on that Benz - when done, retire. Liar, he went over a Million miles by 30k....He gave the car to his landscape feller...with cases of Castrol, filters, and Gold Dunhill Lighter.
"Lighter was always in that Benz, not right to remove it".
My truck is a '93 with 136K. Except for dealer oil changes when new, Castrol 5w-30. I have used Castrol Syntec 0w-30, have used Syntec 5w-30, run the blend too. Hey, I was gettng the Castrol in trade along with the Wix filters, my preference , with AC Delco being the next choice.
Mine seems to prefer Dino over Syn for some odd reason...does not use oil b/t changes. For my long hauls , I prefer to run the Synthetic, or at least a Syntec blend. I had two cases of GTX 5w-30 exchanged for services rendered last time ( out of Syntec at the time) *shrug* it'll run...not going to worry about it.
Best kept secret is Chevron and Havoline - dino , synthetic blend or synthetic. One of my "road vehicles" used nothing but Havoline, Supplier out of Castrol and Havoline more ready avail where this vehicle kept, so mechanic just ordered a pallet for "these vehicles" he kept up with.
One of "our" Camry's , a 4 banger, made it to 200k miles with Havoline Dino 5w-30 until it was wrecked, engine fine, just the rest of the car allergic to snow covered ditches...
"Earl ain't Esso" is my book.