Going from Synth to Dino question.
 

I've got a 911 SC and am switching from Mobil 1 to Brad Penn. Could anyone recommend a weight? I live in N. California and it'll get down to freezing this winter, but then back up to 90 during the summer. Thanks.

Your owners manual probably states 20W50 in summer and a lesser weight like 15W40 in winter. If you don't have the manual you can do a search to find the info in a variety of posts or maybe someone with an SC can chime in with the correct info.
My car is stored inside and rarely sees below 40 degrees so I run 20W50 Brad Penn year round.

Great choice Andre, your engine will thank you!

most of us in the pac nor wet use 20-50 BP if the car is garaged on the days we arent driving in the winter up here...you should be ok if doing the same otherwise if it is outside at nite you might be better off with the 15-40 stuff

Does this help any?

http://www.sinclairmfg.com/fred/911/...e_vs_temps.jpg

source: '84 911 manual

Looks like 20W-50 would be ok.

I'll just chime in and say when I went from Royal Purple full synthetic 20/50 to Brad Penn 20/50 my 83 SC engine leaked like crazy. Surely your mileage will vary, but maybe throw down some cardboard or something if you're parking in your garage, just in case.