Originally Posted By: Win
The majors absolutely can tell if it is their additive package in a stations tanks, and they can, and do, sample branded stations to make sure the right product is in the tanks.
When I was working in Shell servos, Shell would keep track of purchases, and tank volumes.
If they had a suspect dealer, they might send a truck over unscheduled, and see how much residual volume really was in the tanks, as the driver needs to dip before dropping.