That is a good question. It had me concerned when i was deciding on the right engine. I was worried it would be too much.
As it turns out i used the tank that comes with the model (I forget how many CC's it is) but i get flights 13-15 minutes, and i run my engine on the rich side a bit. In the end, fuel consuption was never a problem for me. I use Cool Power 10%.

I was also concerned it would be over powered with a 120 AX and wondered if i should use a 120 FS. After flying so much i now know the 120 AX is a perfect fit. I kind of think I would not be satisfied with a 120 FS, but I'm sure it would fly just fine with one. And there is no reason to think someone would be making a bad choice to use a 120 Four Stroke.