Does anyone know what grade of oil l should be using in my 2002 BMW 325ci now that winter is approaching here in New York

10W30 weight oil should be fine if it can as long as it is good quality oil. 10W40 will also work well.

cooking

Are you talking about New York City or New York State? l would suggest using 5W - 30 in the Buffalo, N.Y. area during colder winter months when the temperatures never go above freezing. How many miles are on your car? How often do you change oil in your 325Ci?

Castrol full synthetic is recommended at 10w30 year round with a change every 15,000 miles.

ANy synthetic oil is fine. You can even get away with using regular oil if your in a tight budget. No harm will be done just that the variable cam wil be a bit slow to kick in..