An update has changed the value of how many coins you will need to complete your refills. The first solar system is the easiest to get this. Once you deplete your fuel, a flashing button near your fuel gauge will pop up and prompt you to purchase more fuel. Click the button to refill. Once refilled, deplete your fuel again, the hit the refuel button. Hit the refuel button a total of five times during one flight to get the achievement. The following are the new values since the update:
1st refuel: 10 coins
2nd refuel: 25 coins
3rd refuel: 50 coins
4th refuel: 75 coins
5th refuel: 75 coins
You'll need a total of 235 coins.