As per above ,(i've always worked it out this way), my m35 gets 12-12.5 litres around town(sunshine Coast)and 10-10.5 on highway cruising.(sitting on 100-120 ks)
My car has the gcg gt3037 upgrade, with 3" s/steel dump,200cfm hi flow cat and fujitsubo 3" exhaust.I should add i dont baby it, but dont cane it either.It does seem to be slightly better left in the sports tiptronic mode.