In yet another example of why it pays off to make sure you fully understand a company’s terms of service, and pay attention when those policies change, Hertz rental customers should be aware of a new refueling requirement when driving a vehicle less than 75 miles.

Starting July 15, Hertz’s new Express Refueling option at certain locations presents an alternative for drivers on shorter trips, but it’s one that may be unwelcome for people who aren’t used to (or may forget to) get a receipt for gas. Hertz customers should’ve received an update via email recently, reading:

Beginning on 7/15/2015 there will be a new refueling option for Hertz rentals in the United States. This Express Fuel option applies at select locations to rentals during which the entire distance driven is 75 miles or less. If you drive 75 miles or less and do not purchase gas, or purchase gas but fail to produce a receipt, a charge of $13.99 will be applied. If you drive 75 miles or less and produce a receipt of a fuel purchase made during your rental, the $13.99 charge will not be applied.

Consumerist reader Andy is in favor of this, writing that he has often found it tough, while on overnight trips, to find gas stations near airports. He likes the idea of a flat $14 refueling charge, but wondered whether a driver could provide a receipt for as little as $1, if that’s really all it costs to refill a tank, and fulfill the requirement, thus avoiding a $14 charge.

A Hertz spokeswoman confirmed as much to Consumerist.

“If customers anticipate that the cost to fill up will be less than the Express Fuel rate, they are welcome to refuel on their own before returning the car,” she explains. “The gas station receipt simply establishes for us that the customer recently filled up. We believe many customers will value the convenience of a flat refueling rate rather than stopping at a gas station on the way.”

Other Hertz customers aren’t so pleased with the requirement of having to provide a receipt, instead of simply returning the vehicle with a full tank as they did before (which you can still do on longer trips), as a recent thread on the forum FlyerTalk shows.

But as one commenter notes, any customer who’s received a car with a fuel meter that reads “Full” but is actually one or two gallons short knows how frustrating that experience can be.

“We only ask for a receipt with the short-distance rentals (75 miles or less) so that our agents know the customer recently filled up rather than opting for the Express Fuel convenience charge,” the Hertz rep told Consumerist. “Often the gas gauge indicates full following these short trips when it’s actually missing two to three gallons.”

As for the cost of gas if you choose Fuel Express, compared to what you’d pay on your own, let’s do a quick calculation: The average price of gas nationally right now is about $2.78 per gallon, according to AAA. Suppose you’ve got a car that gets around 22 miles per gallon, which is somewhere in the middle between a Prius and a big truck. That comes down to $0.13 per mile driven, according to this handy New York Times calculator. That means if you drove 74 miles and found a gas station, you should spend about $9.62 for gas — well below that $14 Express Fuel option. Of course, any difference could be chalked up to a fee for having Hertz refuel the vehicle.

Again, for some, the price of convenience may be an issue for many who don’t want to deal with finding a gas station. But if you do want to save money and fuel up yourself, don’t forget to bring that receipt with you when you return your car.

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