Rgp,
Everyone has their own opinion on what grades of oil is best.At that price I do not think you will go wrong.I personally only because the workshop I worked in the 70s always used 20/50 duckhams green piss,GTX and many others that I cant remember I think with all agents it was down to price.At the mo still using mineral 20/50 and have no problems with it.Like I said down to preference.
Cheers
Bitsa