The reason why the automotive world has been raving about SkyActiv technology has been how Mazda was able to go ultra efficient hi-compression w/o the need of premium hi-octane petrol.
Hi compression conventional engines can never run on regular fuel w/o detonation/knock/pinging. It's a combination of those volcano shaped pistons, 4-2-1 header, low friction & lightweight components(both to control the hotter temps of hi comp) coupled w/ a Sky tranny that combines the benefits of both dual clutch & CVT....not to mention the stiff & light SkyActiv chassis & frame.
Going premium on a regular engine will prevent ping. But on the Sky that is tuned to run efficiently on regular unleaded w/o the ping, filling up w/ premium & hi-oc will yield you no gains, sorry to bust that octane bubble here.

Plus, not all hi-oc fuels are the same. Some are just spiked w/ boosters like xylene & ethanol to give higher octane ratings, but not necessarily w/ more energy. Some of these boosters are hygrcospic & can cause water accumulation in the fuel system. Others may even cause gum deposits & gunk...not things you'd want. Remember, the Achilles heel of these newer direct injection engines is them being more prone to carbon deposits.
You want proven gains? A JBR or K&N intake will give you a few more horses....a tune like Orange Virus could bring you even more.
In conclusion, you guys will be doing yourselves a favor by just sticking to Shell Fuel Save. Save that premium moolah for mods & not let Mazda have a scapegoat should your fuel system & injectors go berserk on you down the line.
Apologies for the rant, guys.
Happy Motorin'!!!
