Note that the more fuel you carry, the shorter your jump range becomes. The fuel tanks themselves don't add mass, but the fuel you fill them with does
But you can manage that as you see fit. For example, if your ship comes with a 32T tank by default, and you add another 32T tank, you will double your fuel capacity. But if you actually fill up 64T of fuel, your jump range will go down. If you only fill up half of that, your jump range is going to be the same as with only one tank. And by extension, if you only have a quarter of fuel filled, your jump range is gonna increase further.
If you're not deep space exploring, none of this really matters though. But if you are, then this kind of fuel management can be useful to get a higher range. An Asp for example, can do 38LY per jump if you don't have full tanks. But you need to pay attention to your route so that you don't get stranded if your last jump brings you into a system without any scoopable stars in it. So, be careful and pay attention to the galaxy map route. You can use the "map" mode to only display systems with scoopable stars. The only types of stars that are scoopable are: O, B, A, F, G, K, M. So if you only enable those in the "show by color -> star class" list, you know where you can refuel. Fortunately, all those are listed first, so it's easy to quickly turn them on and off. (A quick way to remember which types are scoopable, is to remember the word "KGB FOAM".)
