All comes from the same bucket.  Makes no difference. It's all snake oil and marketing.  

zxspectrum:

 

The N.Z. oil refinery is partly owned by the big oil companies (Caltex, BP, Mobil), and all of the fuel that comes out of it has the exact same additives - because it is the exact same fuel. Can't speak for any imported fuel but any fuel made in NZ, no matter where you buy it from, is the same. Any talk of different additives for different brands is just marketing garbage.

 

98 is imported as that from Western Australia, Gull 98 is 95 plus crappy ethanol.. 

Thanks for all the comments guys.  My reference to supermarket fuels was about Britain & not NZ.

As for the injector cleaner I used on my previous car I think it was Wynns. The car was a Laser with the 1.6 DOHC engine.

After reading the comments I am now wondering if I had something else wrong such as fouled spark plugs caused by a lot of round town driving.  The car would start mis-firing when under load at low revs.  After a few days I would get the tank next to empty go and buy the injector cleaner and a full tank of petrol. 

After that I'd go for a nice long drive some of it in 3 rd gear & plenty of revs and it did seem to work.   Maybe it had nothing to do with fouled injectors though. A day or so later the problem had almost completely disappeared but would come back after a few months.

P.S. And yes, I did change the plugs from time to time!

"After reading the comments I am now wondering if I had something else wrong such as fouled spark plugs caused by a lot of round town driving.  The car would start mis-firing when under load at low revs.  After a few days I would get the tank next to empty go and buy the injector cleaner and a full tank of petrol."

What octane did you use? Maybe the injector cleaner was slightly lifting it and it stopped knocking? 

Something around your timing would have been shot, Like the crank position sensor or maybe something else.

I had an Astra 1.6 ecotec manual thing that would miss down low if you say did a pull in 3rd from 1000-4000RPM. I never found out what it was, I used a brand new genuine coil pack too and fixed all the common issues.
Replaced the coil pack, plugs, gave it an oil change, new tires. Long story short brought it up to spec to then have the engine fail, the loom inside the head had deteriorated and caused it to short out and then take out the ECU.

In BMW's you quite frequently get poor idling or missing down low that can be caused by 2 things, either a vacuum leak or a crank position sensor. When my CPS decided it wouldn't wake up one morning my car ran on 3 cylinders, then 4, then 5 then finally 6. Never did it again.

I had a Toyota Vista (a bit like an old camry) that would not idle properly, the revs keep going up and down when it's idling.

When driving it was fine (though it used a lot of oil very fast!), though it had no power and couldn't climb any hills at 100ks, but can overtake fine.

"After that I'd go for a nice long drive some of it in 3 rd gear & plenty of revs and it did seem to work".

This is why the car performed better, not the Wynns snake oil that you put in at the same time.

I get gull 91 for the mower occasionally just to support them for being a nice self serve self pay no staff outlet.

Cars all get 95 from Z because they run like trash on 91. Im not sure if it was 91 or sitting around that does it to the falcon but it will often run really rough for a while and slowly come right. Putting 95 in and even when parked up for months it starts right up and is smooth (assuming the battery isnt dead) also back when I had the under sized 2 liter skyline it was a dog on 91 needing to downshift massivly on hills to accelerate from 40 to 60, much more power at the lower revs on good stuff so the habit has just stuck to not put the cheap stuff in the car.

Too few places have 95 now, they all seem to have moved to 98, in the case of gull their ethonol blend muck, and mobil and BP all have their own brand of 98 at a signifigant price increase which I dont see the corresponding benifits from (if any at all)

k1w1k1d:

 

"After that I'd go for a nice long drive some of it in 3 rd gear & plenty of revs and it did seem to work".

 

This is why the car performed better, not the Wynns snake oil that you put in at the same time.

 

Yes, I realise that now.  At that time I was doing minimal maintenance on the car & looking to sell it.   I was only doing the necessary stuff such as regular oil & filter changes & changing spark plugs myself.  It may have been a combination of under maintained items!

Each time I've bought a new petrol car, I've done tests with 91 vs 95, and although it's hardly scientific, I definitely got more km from a tank of 95, enough that it made the 95 better value despite it being more expensive. 

This may be partially to do with the type of car I was generally using, but even now with the wife's 1500cc mirage, that  is noticeably more economical on 95. I'm sure it 'feels' better, especially when from pulling from low revs, but it may all be in my head...

I've heard in Japan that 95 is their lower octane, and 98 is more common? Or is that just a myth?

wratterus:

 

Each time I've bought a new petrol car, I've done tests with 91 vs 95, and although it's hardly scientific, I definitely got more km from a tank of 95, enough that it made the 95 better value despite it being more expensive. 

 

This may be partially to do with the type of car I was generally using, but even now with the wife's 1500cc mirage, that  is noticeably more economical on 95. I'm sure it 'feels' better, especially when from pulling from low revs, but it may all be in my head...

I've heard in Japan that 95 is their lower octane, and 98 is more common? Or is that just a myth?

 

The whole RON and octane things mess me up. I think they are all relatively the same just different scales. Like in USA 91 is premium or something and they go as low as 8- something RON. 

https://en.wikipedia.org/wiki/Octane_rating

wratterus:

Each time I've bought a new petrol car, I've done tests with 91 vs 95, and although it's hardly scientific, I definitely got more km from a tank of 95, enough that it made the 95 better value despite it being more expensive. 

This may be partially to do with the type of car I was generally using, but even now with the wife's 1500cc mirage, that  is noticeably more economical on 95. I'm sure it 'feels' better, especially when from pulling from low revs, but it may all be in my head...

I've heard in Japan that 95 is their lower octane, and 98 is more common? Or is that just a myth?

It's confusing. I would have though modern cars would be able to detect knocking and retard the timing to deal with it. However... does that make the combustion less efficient?

Also, I have been told that the cost of producing high octane petrol is no way near so much more expensive than the pump price differential... which is there largely for marketing reasons. If so, and if higher octane can be more efficient, then that sounds like marketing considerations are increasing pollution?