Would it be more expensive to my gas this way?

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Right now Shell gas stations have a sweepstakes going on. Every time you buy their gas with a MasterCard, you are entered into a drawing for a new car.

As I was buying gas there yesterday (self-serve, pay at the pump) it occurred to me that I could get an additional sweepstakes entry by breaking up my purchase into two separate transactions. So I swiped by card, put in ten dollars worth, turned off the pump, printed the receipt, swiped the card again, and topped off the tank. Thus, I had two sweepstakes entries instead of one, for the same tank of gas.

Now if someone took this concept to a ridiculous extreme, he could fill his tank with hundreds of very small purchases like this. (Yes, such a person should probably have his head examined, but work with me on this thought experiment). Theoretically, he would have hundreds of sweepstakes entries for a tankfull of gas, instead of one entry that a normal sane person would have. But in the real world of gas pumps, is the pricing set perfectly, regardless of the size of the purchase?

So I guess my question ultimately concerns the mechanics of a gas station pump.
For the same total amount of gas, would hundreds of small purchases cost any more than one large purchase?

[FatBaldGuy]

Just a WAG, but i would think for purchases of very small amounts ($0.10) or less you would probably get less acurate readings just due to the mechanics of starting and stopping the pump.

You might also have problems with your credit card company refusing to authorize hundreds of tiny transactions from the same location within minutes of each other.

[Danalan]

I see nothing in the official rules against this practice -- but you might want to consider possible consequences. It's quite possible that such odd behavior might cause the computer system controlling your use of the card (either locally or nationally) to deny your further use of the card. This might cause all kind of problems, including a blot on your credit report.

[Quercus]

Not sure about how gas pumps are set up, whether each transaction tends to be a tiny bit over or under. But I do know the big winner would be the credit card company, because the gas station pays the credit card company a fee for each transaction, no matter what the size. And since I assume the number of sweepstakes prizes is fixed, what does the company care how many entries there are? (Likewise the big loser is the gas station).

[Balthisar]

Originally Posted by Quercus

Not sure about how gas pumps are set up, whether each transaction tends to be a tiny bit over or under. But I do know the big winner would be the credit card company, because the gas station pays the credit card company a fee for each transaction, no matter what the size. And since I assume the number of sweepstakes prizes is fixed, what does the company care how many entries there are? (Likewise the big loser is the gas station).

Hmmm... maybe not. Is the Mastercard in question a Shell mastercard? Shell doesn't put their name on Mastercards for free.

[threemae]

Just FYI, the rules of the contest also likely state that no purchase is necessary to win. You could just write in for a contest piece.