Any examples?
Sure...
- Cargo aircraft like the C-47 can usually be loaded with enough cargo to exceed their max. take-off weight if fuelly fueled. Also, depending on the range of the operations, it's simply stupid to lug around huge amounts of excess fuel. It adds fuel consumption/degrades performance, etc. The amount needed for the mission and reserve depending on the nature of the mission is enough and in aircraft like the C-47 it can be significantly less than full fuel load.
- Brewsters in Finland were occasionally flown with 300kgs of fuel which is roughly 70% of the full capacity.
- Curtiss Hawks had 5 hour endurance with tanks topped (600liter capacity like the Brewster). Finns often left the fuselage tank empty which left the capacity of 376liters to the wing tanks. Considering the georaphy of the BoF theater and the target rich enviroment available to the French, I'm sure they used their common sense when fueling their Hawks aswell.
- F2A-3 has a capacity of 240 (!!) gallons. Quite a huge amount of fuel for small fighter with relatively low fuel consumption. They were usually flown with 160 gallons. I sure as hell hope they didn't top the tanks before that infamous first and the last clash with IJN...