i have an AU fairmont and i do regular highway driving. i used to get 7.8-8.2 litres/100km but now its more like 8/6-9.0. since it has been getting 8.6-9.0 i have changed to a 2.5inch exhaust and done all the brake discs and pads except the front discs which were apparently warped but i cant feel that anymore since putting new pads on it so im not sure if they actually need doing? (economy didnt change after doing exhaust or brakes)
the problem i am noticing is that every now and then it the car feels like its suddenly lost power or getting held back, and looking at the instant litres/100km reading on the trip computer, when it does it, it usually goes up to 8-9 litres/100km sticking at 100 going down a slight hill, and more on flat roads/uphills as well. when it feels like its going how it should it reads around 3-4 litres/100km less.
i only notice this because i am very fussy with how my car runs, but it is noticable when it decides to suddenly lose a bit of power/whatever its doing. these tests were done without cruise control on as well.
i have done a service recently as well so i wouldnt think plugs or anything have gotten worn.
its a hard problem to explain but if anyone understands me and has an idea of what it could be please let me know!
Thanks,
Chris