i have a 1988 mazda rx7 with 156,xxx miles. i live in california and its like a nice cool temperature. i dont know what kind of oil to be using in my car though.
1st : make sure you stick with the factor recommended GRADE (like 5w30, etc.). That does NOT change with season or weather, etc.
If you want EXTRA protection, you can always go with synthetics. They are great for cold weather starts and the oil does NOT break down in use. One other advantage that synthetic oils have is that they are MORE EXPENSIVE so they can add more expensive additive (like friction modifiers). Friction modifiers are like soap to water, they lower the friction (good thing).
But if you are diligent with oil change, you can probably get away with regular oil.