Now within a month of driving my Mirage home. Realized that despite due to the low miles it has 3 year old oil in it.

I'm quite a fan of Pennzoil Ultra Platinum. But the 0w20 is almost double the price of 5w30 (46.44 vs 24.97).

Would the 0w20 net me 3+ mpg to have gas savings offset the higher cost of oil? Would this thick an oil be bad to run? Though note PUP 5w30 is possibly the thinnest 5w30 around.