“Quite a few enthusiasts” that have never used premium fuel.
As said before NEVER read any evidence to prove supermarket fuel is inferior, (which it is not)
I do however agree with your oil and waxing observations though.
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I’m certainly guilty of enthusiasm , and spending more money than I should on decent tyres (etc) and I’d be guilty of buying expensive fuel too, if I thought my car would benefit one iota from it . But in the absence of any evidence that it does…
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Retarding the timing from a ‘factory normal’ map for poor fuel, perhaps, but advancing on good fuel? That’d be something else entirely.
Surely that’s exactly the same thing??? It’s just a sliding scale.
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Not really what you want, because the default would be to expect standard fuel, but be able to move backwards towards safety by retarding the timing if it’s not running right.
The alternative is to be able to move forward, away from standard and into danger, if it can detect that the fuel is able to stand the extra timing. The problem there is that there is a very good chance of completely destroying your engine for the simple reason that your knock sensor failed and the ECU thought it had headroom on detonation.
Assuming normal and then having protections to move towards safety is one thing.
Assuming normal and being confident of moving into danger is a very different option.
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Hi John, thanks for your reply. I tend to fill my 2018 2Litre RF with premium unleaded from my local petrol station where both standard and premium are available. I have however used standard from time to time when on holiday etc. Never had any problems or noticed any difference in performance whatever I have put in.
I bought my MX5 when I retired and moved to North Wales a few years ago and my partner and I get as much use out of it summer and winter. Cheers
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I’m sorry I don’t see your argument at all - my position stands.
Normal is subjective. There is no default to only move one way to “safety” because when you use higher octane fuel it will move the other way towards “danger”.
If the fuel is low octane the ignition is retarded, if it’s higher octane the ignition is advanced. As I said, it’s just a sliding scale.
The ECU does not have “intelligence” it is just reacting to input from the knock sensor.
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…when you use higher octane fuel it will move the other way towards “danger”.
High octane just means it’s less likely to detonate. If you put high octane fuel in a low tune engine, there’s no danger, it’s just a waste of money.
Given that the original question was whether there’s any benefit in putting high octane fuel in our cars, and that question has been done to death, (again), I’ll leave you to make your own choice, but I’m not interested in getting into an argument about whether an ECU should or shouldn’t do anything in hypothetical circumstances none of us will ever test or prove.
Have a pleasant bank holiday, guys.
Peace and love, etc.
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I had to stop and re group about what this debate was all about.
I just dug out my original fuel filler flap which states “Unleaded PREMIUM”, i.e 98 RON.
With 95 RON being the MIN standard.
Sooooooo, I guess Mazda “ARE” saying 98 RON is best. (But 95 RON is fine.
I have used both in particular when abroad, so I am going to give 98 RON another go for a period of time to see if I can tell any difference? 
Supermarket fuel of course! 
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I would like to thank everyone for there input on this. I normally use standard 95 as I said in opening post but I think I will run 2 or 3 tanks of the better 98 too see if I notice a difference. As some of you have said the more modern ECU should accommodate the fuel change and adjust accordingly. Thanks for all the advice and I hope everyone is still friends after this debate. Thanks
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Regarding all this talk of knock sensor failure, I don’t see why a modern ecu with obd2 capability would not recognise a faulty or missing knock sensor signal and at least throw a cel code if not enter a safe mode at reduced power or default mode.
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Er, no, not so. I had to check my understanding and you’ll actually find that in the UK 95 is defined as ‘premium unleaded’, whereas 98 is ‘super unleaded’.
JS
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Sorry yes you are correct my mistake 
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The stickers in my ND’s say “UNLEADED PREMIUM - MIN 95 RON”.
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Yeah, 95 is Premium, 98 is Super. I’ve also seen 93 labelled Standard, though not in the UK. Saw all three grades for sale in Denmark, for example.
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Some ECUs are programmed to take advantage of higher octane, some are not. Some engines respond noticeably to other fuel properties, some don’t.
Before retiring in 2013 I spent nearly three decades working in this area of technology for one of the major oil companies. We did many many tests on this using many different cars and engines on dynos, track and road, and with many different fuels.
Octane rating is only one feature of fuel specifications and is effectively a ‘headline’ number that most people recognise, but few understand. Other properties effect things like driveability and responsiveness.
If the user manual/filler cap says 95 RON minimum, that doesn’t by definition mean there is no advantage from running on a 97+ RON premium fuel. It doesn’t cost much to find out if you can tell the difference.
My suggestion is run two full tanks of a decent super unleaded (BP Ultimate or Shell VPower). Then after second tank full, when the low fuel light comes on, fill with regular (Premium) 95. If you don’t notice any difference going back to 95 you have your answer.
I should add, that we did a trial using car that had a strong response to different fuels. We re-engineered the fuel system so that the fuel could be switched over to a different fuel whilst the car was being driven along. Using this and fuels designed to give a range of responses from the car, it became quite clear that some people need a very big difference in performance/driveability before they notice anything. Others pick up on much smaller differences. Some people didn’t notice anything at all.
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I will try this thanks 
My very first post here.
I was lead to believe that on cars with direct injection [which can tend to clog up] high octane was best because it burns cleaner. Im not sure if NC’s have direct injection?
Ive had my NC 3.75 fitted with a stage 2 turbo conversion by BBR GTI, and i did mention about the ‘knock’ sensor’. The answer i was given was that they do work [ to retard the ignition] at low rpm and low loads but not so well at high rpm and high loads so BBR have a setting to run the car on 95 octane which retards the ignition by 2 degrees. So i would think there must be a slight drop in performance.
NC is manifold injection.
Thanks for your reply. I prefer manifold injection as it tends to be more reliable in the long run.
I run a 1.6 NB and the improvement is quite noticeable. Both smoother and sharper for a car with 124k plus. I last filled up in December and can’t remember what’s in it1