2012 Prius manual says use Premium Unleaded. Inside petrol cap says E10 is also suitable. Dealer says he wouldn't put E10 in anything he owns, even a lawnmower Toyota Australia said that the only reason that Premium Unleaded was mentioned, was that this was a common 95 octane fuel used in many countries, whereas 91 unleaded wasn't, but wouldn't say if you could use E10 or regular 91 unleaded, instead he referred me to my dealer. What's the truth?