240 dollars
In this problem, we need to know how many dollars can he save using the loyalty card.
Since we know that Melvin pays 1,679 dollars per liter and 1,439 dollars per liter using the loyalty card.
To solve this problem, we need to subtract 1,439 from 1,679. We get:
1,679 – 1,439 = 240
We get the final answer as: $240 or 240 dollars.
Hope this helps :)