My S5 averages a little under 26mpg for normal day to day use. Best I have had is 33mpg and the worst is 21mpg. Yout tuned S4 will now do a lot less!I’m not worried, I get free fuel
More intrigued and hoping to not spend too much time standing at a pump as it’s my daily.
They are decent figures for a 95 map!
Surely they refilled your tank with the vpower they removed once they were done?