Originally Posted by
ronnyk
Not sure the equation is properly stated. ... Assuming a 16 gallon fill-up that is worth $40, benefit for me is $40-15+$30 = $55, better than 3% return. If I use my TD card, the benefit jumps up to $100 in value.
You're correct on the dollar value, but your "3% return" needs work. Return on what? You're not investing anything, except your time. You can deduct additional costs if you want, for MO purchases, etc. But ultimately your "percentage" return is infinite/meaningless, it's really dollars or dollars per hour.