Is slick 50 engine treatment OK to use in the focus 1.6 Zetec-SE engine?.

im only asking as I used to have a 1.7 VCT Zetec Puma & and was advised not to add it, it had something to do with the bore linings in that engine...

Just double checking before buying some...

Or is the Castrol Magnatec 5W-30 oil just as good for the money?

Cheers folks

Andy