been on the forum since 2006 and you have never seen a thread for oil before christ!
0 - 40w - Bit thin and may leak out bolts on the rocker cover but fine for this engine
5 - 40w - Ideal, nice balance protects down to -20 or so
10 - 40w - what the dealrs use also fine. But 5 - 40 is your best bet
Any fully synthetic will be fine wheather you spend 20 pound or 40 pound the only difference will be in your wallet, unless your planning on keeping the car for over 120000 miles or more than 10 years etc.. (or its a track car too!)