Fuel in a 4x game

[Suicide Junkie]

You could do that...

For each ship, if it is in orbit of a colony, boost experience up to a value that is some combination of the planet's population, conditions and the highest level of entertainment facility present.
If it isn't in orbit of a planet, reduce experience by 5% of its current value.

Adjust XP levels and descriptions as applicable.
Fleet XP would be the combat experience, while ship XP would be morale.

[Xrati]

XP's should be based on the entire battle for a percentage of the base points of that specific battle (planet, base or open space, etc.)with different values for each.
1) enemy ratio ships to yours.
2) enemy ship size vs yours.
3) damage taken.
4) ships destroyed.
5) ships captured.
6) ships lost.
Each catagory would provide a percentage of the base XP cost of a battle. Where the total might not add up to 100% of the XPs awarded for that battle. (I hope this make some sense?)

I beleive what they tried to do with the scout ships returning to a supply point is to reflect the food/perishables that might not be found in any other form. Unless you have replicator (STNG) tech, you will need food and water along with necessities.