Everyone does this question the first time. Many anecdotes of other motorcyclists terrified me: gasoline sucks, you can't find it, it's expensive ... Although I had a bike with 30 liters of tank, I felt a little worried. I also bought a 3-liter can that I always left full. I was so worried that I didn't want to leave anything to chance, I studied the way on google and I have marked all the gas stations on my GPS, I even went to certify the existence of each one on google street view, paranoid stuff.
Well, this picturesque photo of the Susques gas station in Argentina does not even represent the 0.01% of gas stations in Argentina and Chile, certain that in small remote villages it may well be that they are all like this, but in general I was amazed, as long as you look at the YPF Argentina national gasoline network website and the COPEC Chilean national gasoline network website. Almost all gas stations have free wifi, cappuccino and brioche is like in Italy, they are always very nice. Then practically there is a gas station every 200 km (125 miles), but do not be fooled by this abundance of structure, at least not in Argentina, normally YPF is cheaper, but there is always a line, and there is no gasoline sometimes, especially in Patagonia. My advice is to always keep an eye on the level and not go around dry or at the fuel limit, when you see that you have at most 200 km of autonomy, look for a gas station.
Moral of the story, YOU DO NOT HAVE TO WORRY TOO MUCH, if there is a road, there is a vehicle, if there is a vehicle, sooner or later you will find some petrol. just organize yourself. But if you decide to go off-road, go into the desert or stuff like that, then equipped with more cans and maybe with fuel bladder for transporting extra fuel and water.