OW-40 or 5W-30

[jackaroo]

Here are some mobil 1 product data sheets:
5w50:
http://www.mobil.com/Australia-Engli...bil1_5W-50.asp
0w40:
http://www.mobil.com/Australia-Engli...bil1_0W-40.asp

Note the higher HTHS figure(high temp, high shear) of the 5w50 mix