Douglas, don't fail to consider that the manufacturer's oil-viscosity recommendations in the US are substantially influenced by fuel-economy factors, AKA the feds' CAFE calculations and requirements. The difference in economy between a SAE hot-30 and -40 may be only a tenth of an MPG, but it all adds up for these manufacturers. Many manufacturers recommend lots thicker oils in other countries for THE SAME engine. (The next time I see that thread--about Toyotas--I'll bookmark it.)
In climates that virtually never see temps as low as freezing, I'd be using at least a 5W-40, and in the summer, I'd use probably a 10W-40.
I'm using Porsche's recommended M1 0W-40 in my Cayenne Turbo now, but I'll soon be doing exactly what I recommend above for you--5W-40 in the 'winter' and 10W-40 in the summer. I'll be changing about every 10,000 miles, HALF of Porsche's recommendation, so this will be easy for me.
I'm going with Red Line, BTW.