IMO opinion, 15 or 20/50 is appropriate for the hottest, most arid summer regions.

In NA and Euro its hard to beat 0W or 5W/40.

Go to Mobil's site and look at a temp service chart.

__________________
Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)