I live in Syracuse, NY so the flow factor in winter would help me, although like you said it would be expensive. I think I also have a cooler. The fluid flows in and out of the bottom of the radiator via 2 hoses. I was curious if the transmission shifted any smoother using synthetics. My 03 X used the Mercon V, but my '06 uses Mercon....I'm not sure if it's partly synthetic or not. I'll have to look into that. Thanks.