I'm not against mixing oils or mixing dino with synthetic. But I am still left with the question of why? 10W40 would cover your range for the next 2-4 months, by that time you should be ready for your next oil change and you can switch to 20W50 for the summer. But since you live in FL and the temp barely gets below 32 you could always run 20w50 with no problems. So why bother mixing. Just crack the top of your favorite oil and pour away.