The endless amateurish debate about the merits of petrol and referrals to SpewTube don't reflect real world experiences, certainly one should not be eyeballing US-style driving as opposed to Australian.
Some points to take note of.
If you are expecting to note a difference, big or small, with a tank or two of 95 or 98, you are going to be disappointed.
If you are a leadfoot only interested in speed and 'performance', again you are going to be disappointed.
If you are a long distance traveller and use 95 , 98 or 100 persistently, a lot of things will improve. It is not a one-hit wonder that many arrogantly assume.
I switched to using 98 in a VZ (3.6 Alloytec), in use continuously from 2010 until late October 2019. Economy went from 10.3L/100km when I first go it, to 6.8 to 7.5L/100 (highway/freeway) on 3 trips around Australia. It was still recording this with tiny variations when it was sold off with 195,300km clocked. The VF SiDi engine is an entirely different beast and not shy of sending up its older cousins.
95 and 98 are hot fuels and provide easier starting in very cold conditions and smooth idle, all things else being equal. It will not cure misfires, not will it increase engine power first off. In Alloytec V6 engines, persistent use of 95/98 will scrupulously clean just about anything in contact with the high combustion temperatures. On the other hand, in SiDi V6 engines, 95/98 will improve performance over time, but will not result in a clean-burning engine, because the nature of the engine — the design, does not afford it (Alloytecs = ported injection; SiDi = direct injection, hence their ever-present sooty nature). True, plugs will be 'wiped' on long, high speed runs but they will soot-up again the moment you go back to frequent burns around the burbs. On Alloytec engines, plugs will be grey-white on removal after a long trip. On SiDi, they will be quite sooty. The requirement for PL/IR plugs in these engines is a hedge against the high temperature and build up of soot: it is harder for it to adhere to PL/IR materials.
As before I use 98 in the SiDi and get anything from 4.3 to 6.4L/100 on short highway/freeway jaunts, and down to 3.9/100 on much longer drives e.g. Victoria to Alice Springs. It's not about being lead-footed or racing the clock: anything like that is a waste of money.
91 and E10 offer no proven advantage in modern engines, despite E10 and E85 having a higher power rating, the economy of either/both is poor and will result in more frequent refills.
The takeaway is don't kid yourself that a couple of tanks of premium will be the wonder kick in the pants a performance car needs after years of running on Uncle's Soup (91) or meth (E10/ E85). The benefits of premium petrol will only become obvious after a lot of driving and observation. This is no doubt the reason premium gets so much negative feedback because the expectation of drivers is unrealistic!
Persistence is key.
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