I would pass on doing the deferred interest option. I decided to try it out a few months ago and no matter how hard I tried, my payments would always be allocated towards promotional purchases (deferred interest). I am not sure if any of you have had any luck, but it was laughable to me. The first time it happened, I changed the settings to pay non-promotional first (like what OP said) and the rep from Synchrony re-allocated my payments which was really nice of them.
But then it kept doing it! Just for kicks, I made a $30 payment (well under my non-promotional balance) to see it happen and sure enough, the whole amount was applied to the promotional. Instead of arguing with the reps, I just paid it off but I am pissed that I lost my 5%! Maybe the system hates me? Not sure, but definetly something wrong in the system and I am not going to lose my store card by bitching about it to them.
