Never seen a sign like that before.
I use 91 in all of my stuff(lawn mowers, trimmers, chain saw, motor cycles, boat, side by side) but never in my 2 gas vehicles, they get whatever is the cheapest, as I will not keep them for 10 years or more like I will my small engine stuff.
I'll take a pic on my way home if I remember. It's been there for years. Super faded.
