Just received this offer by email for my American Express Air Miles Platinum.
Filling up could bring you closer to a future flight. Welcome to the first offer in the American Express Soar into More program.
Between June 1 - July 31, 2017, when you use your enrolled American Express®* AIR MILES® Card to make purchases that total $200 or more (in a single purchase or cumulative purchases) at eligible gas stations in Canada, you could earn 400 Bonus Miles! That’s on top of the Miles you already earn using your American Express AIR MILES Card!
Enrollment is required: Only the first 50,000 eligible Basic American Express AIR MILES Consumer and Small Business Cards to successfully enroll between May 15 - May 22, 2017 are eligible for this offer.1 So don't miss out – enroll today.
I value AIR MILES at a minimum of 10.5˘ each (wich is what I would get if I switched to Cash Miles) so this bonus alone is worth $42 to me.
The return on that $200 "gas" spend will be 420 AIR MILES, or 22.05% based on the above valuation.
The enrollment deadline is May 22nd, 2017.