Quick update !
I always use MRA Navigation in Offline mode.
I tried to put it online and then return it to offline mode and now I have this icon back on my screen showing the distance of the next fuel station.
But it looks like it is little different than before.
I'm pretty sure that some times ago, it was always showing information about the next one in front of us on our route.
Now (and it is like that Online or offline), I can see the distance to the next one, so it is decreasing until I get there.
But, when there (0 Km remaining), I see it incresing considering that I'm getting away from it. So it is always showing the nearest one no matter if it is in front or back from us. As soon as the one in front of me is nearest than the one behind, it changes the distance according to that new one.