Just got around to replacing the coolant expansion tank. Boy, it is nice to have a genuine part that fits like a glove! The Samer one I replaced didn't exactly sit perfectly on the tray nor did the latch that secures the tank to it fit nicely either. But that was not the reason I replaced it. The threads where the cap screws on went out of wack after less than a year. The cap wouldn't screw on securely so had to get a new tank. Anyway, I mixed PEAK concentrate with distilled water, 50/50, using an empty Peak bottle. I used one of those plastic disposable cups (16 oz) to measure--one cup distilled water, then one cup concentrate, and I repeated this step maybe once or twice. BUT, after pouring the mix into the tank I soon realized that I forgot to give the bottle a good shake to mix the water and coolant. Is it okay not to shake the mix? Coolant and water is not like an oil mix where you get oil on top and water below?