With fuel prices ripping massive holes in pockets all over the place, fuel price comparison sites are also be getting one helluva workout.

While sites like FuelWatch don’t reduce the pain at the bowser, they do give you some control over where you’re going to spend.

However, for those that have never been petrol-savvy until this week (hey, same), there’s an app that you need to know about that can do one better.

The My 7-Eleven app allows you to compare petrol prices at 7Eleven petrol stations close to you and get this: you can lock-in the lowest fuel price for seven days.

A reminder of the app’s existence was posted to Reddit over the weekend in a chat thread about petrol prices.

“On the cheapest day, you can scan your nearest 7-Eleven petrol stations for the cheapest price and lock it in for 7 days for use at any 7-Eleven petrol station,” the Redditor explained.

“I got a tank of 98 for 1.94 on a day it was 2.40. Sorry if this is old news but it’s just so bloody cool!”

Another chimed in with a decent saving they’d made using the app’s lock-in feature.

“This, saved $20 yesterday. Just hope that the low days actually come down enough for decent lock-in.”

The 7-Eleven website said that once locked in, “your app will hold your Fuel Lock until its expiry date.”

Other Redditors reminded others that there were other sites that could be useful in comparing prices.

“I use petrolspy.com.au, It works similarly to Google Maps,” said one.

“Also try Motormouth,” offered another. “They have all the metro area covered and colour coded by price which makes it easier to home in on the cheapest station in any given area.”

The My 7-Eleven app is available only on the App Store for iPhone.