at 7.8 its obviously better than 9 on 95 so it does make a difference using 98 with a saver docket its better i got800 from one tank and it still only took 65 litres to fill
with 98 i have got the car down to 7.9 on the highway from sydney and the higher the octane the better the mileage ive used e 10 and that is crap just watch your av go up you can notice the diff but i also use 95 depending on price