No, no, no. You do not need more coolant. If it is below F and L that is normal. The fluid level fluctuates. Also, DO NOT add coolant to what is already in there. If you want different coolant, you have to drain the whole system. Mixing coolants can destroy the cooling efficiency of the coolant and void your warranty. Unless the level drops BELOW the L mark, there is nothing to worry about. The extra room that is between the F and the coolant level is required for fluid expansion. You will need your coolant flushed and replaced between 30,000 and 60,000 miles - depending on driving conditions. Your dealership will know what is est for your car.