I recently bought a case of Schaeffer's Supreme 7000 10W-30 (the store was out of 5W-30). The temperature here in Wisconsin isn't quite as cold as our Canadian friends see; -20/-25°F is about it. Will 10W-30 be acceptable for this application, or should I change to 5W-30 before it starts getting cold? The car is always "garaged"; it was 12°F this morning and it started as though it were 70°F outside. Thanks in advance!