Some of the high volume fuel providers are not toptier, like Walmart for example. Others like Shell and BP only just barely meet the minimum top tier specs. It won't matter very much for the intake valves in the 25-up ecoboosts or the hybrids, but it's a big issue for d-i engines. Then there are the problems associated with carbon on the injectors that mean that you want the highest detergency levels that you can get."Almost ALL gas is 'top tier'" is an easily verifiable (or debunkable) statement.
https://stationfinder.toptiergas.com/
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