Butane Torches

I was told today in the shop that the type of butane you use to refill your ligter makes a difference on how it burns. Something about the impurities in non-premium butane "gums up" the lighter. I believe that to be true and not just a marketing ploy, but if a torch isn't lighting due to bad butane, is there a way to flush it so you can put better butane in and have it return to its original functionality or is that it for that lighter?