If you want the best have a look at the ester based 5w-40 synthetics such as the Silkolene Pro S, Motul 300v.
If you dont want to spend that kind of money have a look at the fuchs titan supersyn 5w-40 and the Motul 8100 5w-40.
http://www.opieoils.co.uk
Cheers
Guy.