The cash price is just a bait and switch pricing. Actually fuel companies really don't care for cash as they have a hire a courier like Brinks to transfer the money to the bank which is not cheap. We used carry a quite a bit of cash in our MH but stopped doing it when we witnessed my sons house burning to the ground and most insurance companies won't pay more than $200.00 for cash lost in a fire. Use mostly plastic and GasBuddy and plan my fuel stops in advance. The prices on diesel fuel can vary up to $.25 a gallon:)