10w30 or 5w40?

[thereur]

Oh no, not another oil question! Sorry.... hope this will be the last. I understand 10w30 is the recommendation in North America, and 5w40 is recommended for everyone else. Northern California rarely gets below 30F in the mornings, and my car is garaged, so 10w30 would seem right. However, wouldn't 5w40 give better start up protection? Also, is CAFE influencing the North American recommendation?

Frank

[repiv]

I think availability is affecting the N. American recommendation. 10W30 can be found virtually everywhere, while 5W40 is found in far fewer places. I don't think you can go wrong with either and the start up protection you speak of would be of marginal difference, especially if you go with a full synthetic.
During some very cold winters when I used to park my car outside overnight at work, I used 5W30 synthetic thinking that ultra cold cranking would be much better. 10W30 flows almost as well in extreme cold and that's all I use now. I think people over-obsess about that 5 point difference on the "W" rating. A few daily drivers around here use 10W30 dino oil all winter with no adverse consequences. Use whatever is easiest for you to get.

[thereur]

Obsess less! Good! Whew. ;)

Between going through your old posts, and answering my questions, you've been a big help in helping me understand the car. Thanks very much, Dave!