Motor Oil?

I just bought a 97 318ic, and did not know how old the motor oil was, so I asked my wife to bring it to a shop to have it changed. The shop put 10W 30 in it, but the owners manual says to use 15W40 in this climate. Will it matter to run the 10W30 for awhile?

Also, what brand is best for a BMW? The car has 87K miles, and I don't know what's used over the past 10 years.

I live in S.E. Virginia and I have always used 20W50, i understand coler climates might dictate a lighter oil, however from +15F to +101F my oil weight is 20W50.

what brand oil do you use?

I use Amsoil 20W50.

Mobil 1 is a good brand as well, and a bit less expensive than Amsoil.