Tank fuel is limited, but can be replenished by destroying enemies. A tank is destroyed by being shot by an enemy, getting caught in the midst of a force field (running into it from the side is safe), and running out of fuel.
Tank fuel is scarce, but can be restored by vanquishing enemies. Tanks are destroyed through being fired upon by opponents, encountering a force field (side-on collisions are safe), or running out of fuel.