Just to be clear...there is absolutely no reason to level up tanks that are in your reserve if they are going to remain there and not transition into your main platoon. I mean, I suppose I can think of ONE benefit, and that's to have a roster to run missions while your main platoon is repairing, but if you have to repair it's because you used your limited oil to level up tanks that weren't in the main platoon. With the commander level gap still likely affecting you, this is the worst thing you could possibly do.