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simple question, what octane fuel does the NB8A require?

I have been filling with 95ron fuel, but does the NB8A ECU have maps for 98ron?


probably a stupid question, but it's not in the manual.

Pretty sure it's only mapped for 91. Higher octane won't give you more power, but may give you better fuel economy.

My NB8A will only run on 98 octane, anything less and it runs like a slug.

Your vehicle manual should tell you the answer. Pretty sure mine says 91 RON for the NA6. I have been using mostly 91 with the odd tank of 95 to help keep the injectors clean. Then for track days I give it a tank of 98 for extra protection against high rev pinging. No idea if it is really necessary but it's cheap insurance.

NB8A will run on 91 Octane no problems. But the higher the better.

One thing though...Mazda does not recommend fuel with Ethanol on the NA-NB.

I use 98, better for the engine, engine performs better, not sluggish.

And it's only ~$4 ontop of a normal tank of 91 octane, so why not.

philz wrote:I use 98, better for the engine, engine performs better, not sluggish.

And it's only ~$4 ontop of a normal tank of 91 octane, so why not.

i paid nothing extra today

so why not

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i usually fill with 98 anyway

I rather piss in my tank than fill up with Shell.

They are mapped for 91 but I always ran 98 in mine..... seemes happier I reckon!

Guran has the key and that is refer to the owners manual or get one second hand / new. The manuf advises what fuel to run on. Paying for a higher RON is money out of the pocket- if you are doing the nations average 16k km.then an upgrade from 91 to 95 will cost abt $128 and 91 to 98 $240. The oil co's are the winners. Same logic for oil- pay extra if you want but Mazda are not going to recommend a spec without knowing that it will do the job. Tests run on fuel economy and different fuels recently by Drive on identical cars showed stop watch performance was virtually identical though one conclusion was that E10 is not a good choice ( paraphrasing)

I've filled up with each grade from a completely empty tank and used the trip meter ( aka onboard computer ) to see the difference in economy/kms per tank, and the 98ron came in at 346km vs 95ron @ 320km vs 91ron @ 297km.

I think I have the rons correct?? Anyway, nothing terribly scientific but I will be paying the extra $ as the difference isn't subtle.

As for performance, I get a few extra BHP depending on what I wear on the day...

and the 98ron came in at 346km

........ are you a hard driver??? - I use 98 fuel and get 520 Km per tank combined city and highway driving.

the way to check fuel economy is by checking how may km you do and how many litres you use to fill the tank between fill ups. So you set the odo when you refill - drive the car - refill and record the KM the litres used and reset again for the next check. The formulae and an example- you do 400km and you use 32 litres. Litres X100 / km travelled 32X100/400= 8litres per 100km. That is the standard metric measure for fuel consumption. The km travelled by Ando on a reportedly empty tank to a full one suggest that this car is drinking a lot of fuel. The 8l/100 is quite achievable on Mazda's recommended octane rating.

Well, I thought it wasn't the most fuel efficient car I've ever had... That was why I was doing the economy tests. It's my first MX-5 and I thought it may be normal given it prefers to be revved hard to get torque. I'm at a loss as to why it seems to drink so much? I'm glad you guys chimed in! Hopefully we can get to the bottom of this?

I was on the M2 today and at 100 kph it sat on 3000 rpm in 5th. Does this sound right??

Ando wrote:I was on the M2 today and at 100 kph it sat on 3000 rpm in 5th. Does this sound right??

Sounds fine, I'm getting around 450-500 a tank normally as well on 95.
General guide for cruising gears, 40-3rd, 50/60-4th, 70+-5th