My driving instructor (I took 3 classes with him back in 1993) told us once in a while use Petro Canada 91 (3 times 87 then one time 91), he told us the additive can clean car engine.
Sorry, I didn't read your posting clearly.
It seems that you want "air" miles for free air ticket in future (maybe I am wrong again). If that is the case, my point is that you have to spend an extra of xyz cents, before you can have extra xxx air miles. And that extra xxx air miles is equivalent to ABC dollars, the cost of that free air ticket. Is the extra xyz cents you spent to get extra xxx air miles less than ABC dollars. If not, I don't think that is a good deal.
Besides, you have total control on how to spend money in your pocket (xyz cents), and you have limited control on how you can spend those air miles.
Money in your pocket has flexibility (how, when and what to spend).