Can`t speak for Sunoco (yet), but I have run 3 year old VP C12 with no issues, performance wise, however, when I was racing my NHRA Stock Eliminator Mustang, we had to go thru NHRA Fuel Testing several times per event, and I had some C12 from my 55 gallon barrel, that wasn`t even a year old yet, that barely passed, and the fuel tech suggested that I buy some fresh C12 from the VP trailer at the National event that I was at, which passed fine, even though the ET slip showed no improvement. That said, a few weeks earlier, at a NHRA Divisional race,that same batch of fuel passed easily. Funny thing is, a buddy was racing his 65 Impala Stocker at that same race, and he doesn`t run his car very much, and his C12 passed OK, even after sitting in the cars factory (vented) gas tank for 3 years, go figure. I don`t have the Stocker anymore, so I don`t need to worry about fuel check anymore, and I now have a barrel of Sunoco Supreme that I am running in my Fairmont, that was new last year, but I also have a couple of 5 gallon cans of Sunoco Standard which I bought in 2022, that I hope to run this year. I have never tried race gas that was 5 years old, but my buddy has used some 3-4 year VP C12 on the Dyno, and it seemed OK. I have never had race gas "go bad", so I have no idea if it gets a bad smell like stale pump gas does or not. If it smells normal, and looks clear, I would likely give it a try. But I would certainly want to use it up soon. Or maybe you could mix the old gas with some new gas of the same grade.