I flushed/drained my radiator the other day, replaced all the hoses, bought 3 gallons distilled water and 3 gallons prestone since the owners manual says the coolant capacity is 6 gallons. I was only able to get 3 gallons of coolant and 2 gallons of water into the truck, what gives? (I even drove the truck for awhile to get the temp up and thermostat open thinking maybe that the engine had to be at operating temp before the coolant could fill up the engine pasages. Is this ratio of coolant to water OK? (66% antifreeze)