Giving customers the ability to pay for gasoline at the pump using a mobile app is an ideal solution: encrypted mobile payments are more secure than magnetic-stripe cards, and card-skimmer crooks haven’t (yet) found a way to intercept payment information. ExxonMobil has added mobile payments to their pumps, but with a catch: you have to use their app instead of your mobile wallet, and that app is iPhone-only.

The good news, as far as Exxon and Mobil station operators are concerned, is that that this means they don’t have to install any additional equipment. Instead of outfitting every pump with a new payment terminal with NFC readers, they just had to roll out a software upgrade to the payment terminals that they already have.

That’s an important difference, since, as Harry McCracken points out over at Fast Company, such upgrades would cost each station somewhere between $30,000 and $40,000. The company doesn’t own individual stations, remember. They would also need to have at least one pump at a time out of commission for upgrades.

If ExxonMobil volunteered to cover the expense, keep in mind that the company has almost 10,000 stations, which would make the project cost up to $400 million. Payment by app is important to customers and station operators, but probably not that important.

The way the app works is simple: it recognizes that you’re sitting in or very near an Exxon or Mobil station using GPS, and then you authorize the payment using Apple Pay. You can lock payment cards and your phone in the car if you want to, since you won’t need them while pumping.

There’s no word on an Android version, or a version compatible with any of the numerous other mobile wallet apps.

Apple Pay Arrives At ExxonMobil Gas Stations—With A Twist [FastCompany]

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