Ok, here's the details. I have a 70 Monte Carlo that gets stored in an unheated unit for the winter. I change the oil as soon as it comes home and right before storage (overkill, maybe, but that's what I do). I use Valvoline 10W30 and a Wix oil filter. I do not know the engine internal specifics since I didn't do any engine work when I got the car or since. I bought the car in 2005 and have done this every year. Depending on how many miles I drive, I may change it again in the summer. I doubt I go over 3,000 miles in a year.