High octane petrol

[Steampunk]

But having said all that ......
I think the general concensus is running PULP on a car that technically does not need PULP is the cheapest insurance you pay for to help prolong the life of your engine.

[bigdog]

Whoa! Big call 1red... I am not aware of any wear prevention arising from different fuel use- oils yes, but fuel does very little lubricating in the combustion process, and the 'cleaning' properties of hi RON fuels relate to keeping the combustion chamber free of carbon build up. I have seen very little carbon build up in any of the motors i have rebuilt over the years, regardless of what fuel they were running on. I really doubt that running hi RON fuels in engines that don't need them has any beneficial effect other than a very, very small power gain and maybe a slight gain in fuel economy in certain cars (depends on the state of the engine and the computer's ability to adapt to the different fuel). It seems that many NA owners have experienced good improvements in economy running 98 RON, but that must be weighed against the extra 10c+ per litre..... again I doubt you would come out ahead. I did the tests and sums on my 5.7 Commodore and concluded that 91 RON was the best alternative, and it used significantly more fuel than an MX5...

[Benny]

I think that part of the reason that you use less fuel when running PULP as against normal 91 RON, is that most 91 RON fuels have up to 10% ethanol in them, and this measureably increases fuel consumption as ethanol does not have as much energy per litre as petrol does, so you have to use more.
Sometimes, it's possible that using PULP instead of standard, could in fact, cost you less as you would need less of it.

[bruce]

Plus, how long do you guys keep your cars? I wouldn't be that worried about motor longetivity.

[Damo]

Internal combustion petrol engines make the best power JUST on the verge of detonation. Using a higher RON fuel will raise the detonation threshold, thus you won't make as much power.

I believe this is correct and so in none of my other (older) cars have I used premium but my question with the MX-5 is whether there is no detonation on regular because the engine settings are fine for it or it is because the computer has retarded timing because of the knock sensor. That is whether the computer will adapt to higher octane fuel or it will just try to prevent damage if you get a tank of fuel that is worse than regular should be.

[Steampunk]

Whoa! Big call 1red... I am not aware of any wear prevention arising from different fuel use- oils yes, but fuel does very little lubricating in the combustion process, and the 'cleaning' properties of hi RON fuels relate to keeping the combustion chamber free of carbon build up.

I didn't mean it that way Monsieur BD, I meant prolonging engine life by virtue of minimising the chance of pre-ignition by using higher RON fuel.

Damo, NA's don't come with knock sensors, not sure bout NB's, and if they do, then yes, the engine will sense a "knock" and retard timing straight away.
B6 and BP naturally aspirated engines have above-average compression ratios, but it's nowhere near what some other engines are making, and well within the safety-zone to operate with 91RON (or even less) fuel.

Don't forget, knocking or pinging will be detected by the knock sensor (if your car has one) long before it becomes audible to the human ear. If you hear the "marbles shaking in a can" sound, then that is very bad knock/pinging.