Here's a little 'hair-splitting' for us*. Porsche seems to be in love with Mobil 1 engineoil. For the Cayenne V8s, P recommends 0W-40 for all temps and 5W-40 and 5W-50 for temps above -13dF. I live in Phoenix which gets REALLY hot in the summer; I've seen many days of 120dF.+ air temps above the pavement, and the LOWS get down to about 85dF. in June - August. I've settled on Red Line 5W-40 for nonsummer** use but am undecided what I should use for the summer fill; I'll be doing 2 changes per year. I'm thinking that RL's 10W-40 might be a better choice for summer since it has NO Viscosity-Index Improvers, but its slightly lower 100dC viscosity of 14.6 v. the 5W's 15.1 points me toward the 5W. The oils' HT/HS viscosities of 4.7 (10W) and 4.6 are virtually identical as are their warm viscosities of 94 (5W) and 98. 'VII-less' 10W-40 in the summer or 5W-40 all year? * WOW do we get caught up in the nonsensical minutia of this stuff! ** It's never winter here; it's just not summer for 6 months a year.