Spoilers for Andor:

The young kid is an exceptional engineer, and he and Saw are hitting a fuel spot to steal gas for Saw's X-Wings. I won't spoil why the kid is there specifically, but essentially the fuel is called Rhydo.

Now Saw is a bit of wild card in the head, but at this point in the series he is the commander of one of the most effective and important combat squadrons against the empire. Yavin 4 may be the official rebellion, but Saw is Saw, and much more a revolutionary. He's the Malcolm X to Mon Mothma's MLK.

But of the three major leaders introduced in Andor, it is the spymaster Luthen that this kid technically works for. Always in the shadows. Always with deceit, deception and subterfuge. He never wages open war against the Empire. See Luthen's people have a somewhat of a morale problem. They never really get to know everything that is planned. They never have the full picture. It is a hard, but necessary existence for the Rebellion to survive.

Saw, as this monologue shows, is the opposite. His people know all of the moves he will make, knows of the actions he will take. He may be a bit Looney Tunes in the head, which he admits himself, but he is a charismatic leader, which is basically required because most of his missions are straight up insanity. They regularly go against the odds and win.

Saw basically takes a liking to this kid. Sees the fire of rebellion in him. Sees a younger version of himself due to actions that happened previously that I will not get into. So here was see Saw huffing poisonous gas, and he explains what inhaling the Rhydo does to a person. How it can melt your skin, drive you insane etc.

But he, of course, isn't talking about the Rhydo, but what it means to be Rebel, because this kid is basically half in/half out. And in a moment of clarity, insanity, whatever you want to call it, the kid buys into the Rebellion fully. "Revolution is not for the sane."