A few years ago when Google Now was officially introduced, it wasn't as impressive as it is today, but only because it didn't actually offer anywhere near the same amount of stuff. Google Now is great for just about anything it seems these days, from keeping you up to date on your travel itinerary to posting the most recent scores for games from your favorite sports teams, and it can even show you the last location of where you parked your car, all of which may soon be capable without a data connection. As Google continues its ongoing mission to make Google Now as useful as possible, they appear to be rolling out a new set of cards which will allow people to be alerted with a reminder to refuel a vehicle at a gas station.
To be clear, according to the user who received the card pop up in Google Now, the card showed refueling options for different gas stations because the user was returning a rental car in that particular area which Google mentions in small text at the bottom of the card, and when you return rental cars you're supposed to refuel them, so, this would seem like a good reason for a card alert that reminds the customer to make sure the gas tank is topped up before returning the car to place from which they rented it.
When the card pops up, it's labeled as "refueling options," and under it gives a small picture of the area in Maps, with listings for a few different gas stations that are close by, and it lists details like hours of operation as well as the distance from the user. It does not however, list the prices for gas at any locations, so users will still have to look gas stations up for that particular information. Just because prices aren't listed in the gas refueling card right now though does not mean that Google won't work something like that in at a later date as it would be fairly useful. There is no telling whether or not this card will show up for everyone right now, but should you be renting a car anytime in the near future then it may very well pop up for you.