The lower High Temperature High Sheer of 20 weight oils, and googling HTHS wear graph had caused me years ago to permanently (and forever) switch my vehicles to 5W-30.Long story short, I no longer have the corolla. On my shelf I have almost 8 gallons of 5w20. I was going to use it in my truck (f150 5.4 3v) but I've been using 5w30 for a long time. I know it's safe, but it's hard to go back lol
But if I had 8 jugs of 5W-20 laying around, and my vehicles were speced for 5W-20, I would use them up to save the money. There are so many of those Ford LTD taxi cabs in small towns that have 400,000 miles that were on 5W-20 since new.