i got some free redex from the birmingham car show a couple of years ago, i noticed no difference when i used it.
my car is a 2000 fiesta zetec 1.25.
according to the first google for fuel calculator, i put in £5 fuel at £117.9 and get 45 miles out of it.
"Your real-world MPG average is 48.24, covering 45 miles using 0.93 gallons of fuel."
i dont do any motorways or A roads just 3 mile journeys to and from work and friends houses.
i dont drive like a granny but try to be as easy as i can on the pedal.