I have an OTR, Tune, Headers, High flow cats, straight through exhaust and average 12.5l/100klm at approx 50kph average speed around town, goes up quite a bit in traffic etc to 14's, before all this was done went to bathurst last year from Brisbane and return on 3 tanks of fuel, aprrox 2500klm, and 225ltr of fuel, average 9.6l/100klm,(since all the mods have seen 8.6l/100 on shorter trips 130klm and this is with a heavy foot at times)all this being said - the price of fuel has had continual increases as well, however it may mean plugs need seeing to, aircleaner, little things that can have some effect, tyre pressures, wheel alignment also, E10 has a higher RON rating but a lower calorific value so it will burn more per lt/klm, I drive mine how I want to and not too concerned about L/klm, not everyone is in the same boat, I have a V8 and if I was worried about the cost of putting fuel in it then I cant afford it!!!check the basics on the car (as above) this could help you get more out of the fuel you put in,