You shouldn't base everything on the temperature of your engine. Sure, it is a good way to help tune, but there are better ways. I would richen it up a hair to be on the safe side. Take this for example. If you have a really good cooling head, you could be way too lean, and have temperature readings of around 250. When you are lean, your engine is getting wrecked each time you drive it. Just my opinion man! Snow driving rocks!