Ive been running 91 octane petrol with fuel system cleaner through my 2005 vz commodore. Do you guys reccommend doing this for fuel economy? Yesterday I left home with 900kms left til empty on the dash. Drove 70km with the cruise control on and admittedly had the aircon going. Got home with 760km left til empty. Surely the aircon wouldnt use that much extra petrol or could it be the low octane petrol? The reason why I'm asking is I'm planning a road trip with not many petrol stations along the way. What does everyone think?