Let's say full tank on my car is just over $120. What is the most economical way to save up big on AA smart fuel:

1) pump 2 $40 at BP (you are allowed to use the pump twice before needing to pay at counter) and save up the discount
2) pump 3 $40 at BP on empty tank (will need to visit counter twice, might cause hold up) and save it all for the next empty tank
3) pump 2 $40 at BP, and repeat next time, to save 4 discounts  and then go in next time on empty

Frankly I haven't bothered because I'm afraid of being frowned upon ... so ... do people do that?