Wrong on 5

premium grade is high in Octane number (R+M), which will tollerate higher compression ratio. It has nothing to do with NOx generation, as the NOx is depending on temperature. Moreover, the EGR system is recirculating some emmission gas to the combustion chamber, and such mix will bring the temperature down during combustion, and therefore reduces NOx. So, the gas grade has nothing to do with NOx, but the EGR system does.