Not sure you guys know this but Marathon uses some type of STP additive in their pump gas.
Marathon's been doing that since 2006. STP's fuel additive is/was a competitor of Chevron's Techron additive. The Marathon/STP relationship
continues to this day.
The STP Gas Treatment you buy across the counter does not contain PEA - it's basically a fairly old formulation
of Stoddard Solvent, petroleum distillates, napthalene, etc.
For Marathon to stay competitive with it's gasoline product, the STP additive in Marathon gas might be something quite different than the STP you can buy. It probably contains PEA. I couldn't find any information on this, but I doubt that they could keep it a secret for long.