no need dyno already can easily feel differences between RON97 and RON95.
btw, if u must pump RON95, try to avoid Shell. its crap

i experience this too on 2 of my cars. both EFi so its not the tuning.

car engines ignition timing will be retarded when knocking happens due to highly combustible low octane fuel, such as RON92 or RON95. retardation of ignition causes less power. this is why racers usually advance the ignition timing to get more power. also too much retardation on the ignition timing indeed DOES cause harm to certain engine parts, commonly is burnt exhaust valves.

so its true as some earlier posts say, save gas money, possibly increase engine wear

This post has been edited by masao343: Oct 23 2012, 11:12 AM

all cars has a range of octane rating that the engine can consume.
eg a vios can go as low as 93. but it will perform better at 95, or 97.
the "car designed for Ron XX" figure is the lowest it can go without dying on u

This post has been edited by masao343: Oct 23 2012, 11:56 AM

just like the lady (vicky?) on Topgear said in her comparison on the different RON fuels, it does have a difference, although most average auntie/uncle wont notice it. the engine feels more responsive to the throttle press.

i dont think its only you.
coz shell is crappy.
i dont even need to drive the car. i just start it in the morning with shell and the idling is so rough!
with BP or Esso the idling is smooth. happens every morning until i changed the fuel.