I have a 72 LT1 corvette that has Pennzoil 15-40 oil in it now here in Illinois. I may drive it some this winter and the car is stored in a garage. Should I put a thinner oil in it for the winter and which weight?
To be honest, if you're only going to be taking the car out for the occasional pleasure cruise on a nice day, and it's always going to be kept in the garage (which is most likely going to be above 40-50F most of the time) then you could probably just stick to the same oil you use in the summertime without a problem.
I keep 5W30 in my 1970 LT1 that I use about like yankees1, except I do not have a heated garage. I believe the more rapid flow of oil on start-up is better for longevity. I use the same weight all year round, but even in the summer I rarely drive it more than 20 miles. If my use were different I would consider a different weight in the summertime.