I researched this "Top Tier Gas" subject a few years ago. This "grade" of gas suposivly has some extra stuff in it...but for me,especially with my RV, the reality is:
When traveling , say, coast to coast or a long trip that requires on the road fillups, when y'need gas, y'need gas. SOMWHERE...you might find "top tier". Also, IMO,(again reality), it doesn't matter at all if you NEVER get "Top Tier". Gas is gas, comes from the same tank farm and these whatever additives are added to the tanker truck there, depending on the brand.
Here, in beautiful downtown New Jersey, only VALERO has "Top Tier" stickers on their pumps. So...with all the brands available to me...and only 1 brand mentioning it, how important is it?