Why Some Cars Have Gas Tank Fillers on the Left or the Right (2017) (jalopnik.com)

I had an 1985 Oldsmobile Delta 88 Royale Brougham LS with the filler in the middle (behind the license plate).

Somewhere I ran across the bit of trivia that there is often a little triangle/arrow next to the gas pump icon near your fuel gauge that indicates which side your filler is on. But once I started looking for this, I noticed that it isn't universal.