My Prius C takes red coolant. I had it flushed at a car care place 3 weeks ago and he added universal coolant by Auto Zone in the orange jug. Then I got second thoughts and decided to drain it and refill it with Valvoline red coolant made for my car with P-HOAT. I may have left about 1 cup of coolant in the engine before I added the red coolant. Should I have filled the system with water and drained the water before adding the red coolant? I heard some scary stories today about some coolants not mixing well and creating a gel. I kind of hate to do the procedure all over again but I would if it was necessary.