Fokker's your man on the ratios!

He is the Oil Master.
On which is best - to be honest it's a bit like saying which trainers are best out of Nike, Adidas, Asics etc. Meaning that all the leading brands are pretty similar, and make excellent products. Most people tend to use whichever oil their local bike shop sells. But you can't really go wrong with say Putoline, Castrol, Motorex, Silkolene, Maxima, Bel Ray etc - they're all pretty similar to be honest.
So pick whichever brand you can get pretty easily, and stick to it really.
Re which type of oil - do you know which brand you'll be going for, as we can then advise from there.
E.g. - if it's Putoline say then your pre-mix will be either MX5 or MX7 - MX5 is semi-synthetic, MX7 is fully. But I'd personally think you'll be fine with the MX5, and it's a bit cheaper. On the Gearbox side then you need either GP10 or Light Gear - either will do the job fine - more important is how often you change it, so change it regularly and the bike will run great.
