Thanks a lot for all the inputs, I appreciate it. I know my car is aging and has a lot of miles on it and I was planning to change it to something with lower miles. I'm glad I didn't take the plunge since my financial situation started to go south lately unexpectedly. Therefore until I get on my feet again, I have to take good care of my car.
Toyota has often recommended 10,000 mile oil changes when using synthetic 0w20.
Amazon has single 5-quart jugs of Ultra 0w20 for $32 each, Amazon Prime free shipping.
I'd go with Walmart's Pennzoil Platinum (not Ultra) 0w20 for cheap, IF you really want to stick with Pennzoil.
Certainly any 0w20 you see on the shelf would do, but you've got a lot of miles on that aging Scion, so I'd recommend the Walmart Valvoline Maxlife full-synthetic 0w20 which meets dexos1 Gen2 and ACEA A5/B5, and the "High Mileage" formula has some extra seal conditioners to keep those old seals from springing leaks in the future.
I do recommend using a 0w20 over a 5w20 for below zero temperatures. There is a small amount of difference in flow at below zero between the two.
No problem with changing brands of oil.
I thought about using high mileage oils in order to have better protection but I did not for two reasons;
1- I couldn't find full synthetic high mileage oils. I didn't want blend synthetics just to have high mileage additives.
2- I got the car at 129k, at 130k car got a major engine work from Toyota, they changed pistons and pistons rings. Therefore I didn't know if my engine still counts as a regular high mileage engine or not. I heard that once you go high mileage oils it's better to keep changing it with the same high mileage oil with same additives so I didn't want to go that way without searching enough.
Is that oil full synthetic with high mileage properties? Is there anything else like that I can compare?
Thanks again for all the answers, I appreciate it.