fuel for my mk2.5

[Aldi]

It is a fact that the shelf-life of everyday ‘green’ petrol (std 95RON unleaded) is only about 3 months. That’s why I always drain my outboard boat engine every autumn - it just refuses to start if running on ‘old’ petrol of either variety.
That’s in contact with some air - just the space above the fuel level in the tank - even if full - is enough.
The super-unleaded (Shell Nitro etc.) shelf life is longer, but I’m not sure how much.

I can tell the difference quite readily on my 2.0 NC Sport if I switch between the two. I usually run on 97RON, and it loves it.
I have, on occasions, had to use 95 RON, and it feels sluggish by comparison, even giving the occasional ‘pink’ when it first comes through the line. The ECU adapts the ignition timing, or so I’m told, to whatever it gets.
I also use super diesel in my everday hack Freelander, and that gives better (smoother) performance and noticeably better (+10%) eceonomy, but that may be a ‘red herring’ compared to their petrol equivalents.
In the overall scheme of things, no-one buys an MX5 for economy (do they?) so what the heck…pay for the best for your best car, and get the best out of it!
Just my thoughts…

Aldi

[sdg111]

The ECU  will advance the timing with the richer fuel so there’s bound to be a performance difference, no?

I always use Sainsbury’s super unleaded and always notice my NB runs better with it than with ordinary unleaded 

[Jeff_Palmer]

Another vote for Sainsbury’s super unleaded. It’s the closest supplier of 97ron fuel to us. Use Shell nitro plus When I can get it. 

[Paul_W1]

@sdg111

The ECU  will advance the timing with the richer fuel so there’s bound to be a performance difference, no?

No. It doesnt work that way round, I’m afraid.

If your engine has knock sensors, the ECU will retard the ignition if low octane fuel causes pinking.

 

[Art_Tidesco]

@Drumtochty

@Woody

but just thinking about running higher grade fuel for the amount of miles i do a year plus when i leave it for a few weeks/months hopefully

Do you have any factual basis to your statement. I have never seen anything factual on this on the MX5 especially as you assume “plus when i leave it for a few weeks/months hopefully”.

 

I have found no factual back up to that one.

Late to the party, but I have three points to make.

1. Degradation of fuel is mostly down to evaporation of the lighter constituents of the fuel mixture, 

2. Further degradation happens because the lighter constituents will tend to float to the top of a volume of stored fuel, so the heavy constituents, less conducive to quick starting, will be sucked out of a tank that has been stood for any prolonged period first. 

Issues elaborated upon in this BP blurb about fuel storage :- https://www.bp.com/content/dam/bp-country/en_au/media/fuel-news/petrol-life-vehicle-tanks.pdf

3. Any even empty container with a breather that is exposed to major heat changes, such as the fuel tank of a car, will have condensation of water vapour from the air form on the inside walls when it cools, this will weaken the fuel strength over a prolonged time and was the cause of rust that turned to sludge in old skool metal fuel tanks.

Keeping the tank full will minimise the amount of fuel evaporation and the amount of condensation formed.

As an aside to get the best possible fuel quality if I see a tanker at the filling station I generally wait until it has discharged its cargo to get the freshest mix ;-)