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Discussion Starter · #1 ·
Anyone know about the gas in Japan. I have asked lots of the local people but none seem to understand my octane question. I always use the best they got but I am wondering what that is.


Discussion Starter · #2 ·
I believe foreign contries use different methods of measuring. IE here we have 93 octane, they have a different measurement.
I kno in europe they have different measurements.


Never fast enough
331 Posts
I think Japan uses RON ratings, what are the rating numbers you have available? From what I understand 96 RON in Japan, should be about 91-92 here in the U.S. which uses a (RON + MON)/2 rating.

All fuels here as supposed to have high MON ratings, which could mean while the number in RON is less, it might actually be a better fuel for reducing knock.

Research Octane Number [RON] is a low speed, "everyday" type test. Motor Octane Number [MON] is a higher speed, more stressful test. So, RON tests yield higher numbers and MON tests yield lower numbers. Do a search on RON and MON on the internet to find out about the actual tests.

Discussion Starter · #6 ·
There are no numbers at he pump that make any sense. I just always get Supa Purasu (Super Plus). I will look into it more and see if I can find out.

Thanks for the info

5,807 Posts
Pardon me while I revive this super old thread.

Originally posted by [email protected] 17 2005, 12:48 AM
In Europe 98-octane gasoline is common and in Japan even 100-octane is readily available at the pumps, but this octane nomenclature is misleading to Americans as foreign octane ratings are derived entirely differently from our own... So, like every other measurement system it seems that everyone else uses a different scale than we do, but unlike most other instances where we have had the good sense to create different units of measure in this case we all use the same name...
Japan and Europe use a system called RON or Research Octane Number to determine the octane rating of their gasoline, while stateside we use a system called AKI or Anti-Knock Index to determine gasoline's octane rating... Interestingly, to further complicate things it would seem that our own AKI system is actually derived from the average of the RON system and another more complicated system referred to as MON or Motor Octane Number... So, to recap our methodologies for measuring gasoline's octane rating are different, but share some common elements...
So, with the commonality of RON in mind a good rule of thumb is as follows, multiply the foreign RON Octane rating by 0.95 and you will have the US AKI equivalent.

( RON Octane Rating x 0.95 = AKI Octane Rating )
98 RON Octane x 0.95 = 93.1 AKI Octane (US measure)
100 RON Octane x 0.95 = 95 AKI Octane (US measure)

So, as you can see the 93 or 94 octane fuel we are all paying an arm and a leg for is actually quite comparable to the higher octane fuels found in Europe and Japan. The people whom have to worry about low octane rating are our friends out west in places like California that are subjected to substandard 91 octane.
91 AKI Octane (US measure) = 95.5 RON Octane
I bolded what I deem to be the key part of the quote. I actually found this thread through google, as I was trying to find what octane the previous owner was likely using over in Japan. (RHD :tear: )

The Grandfather law (allowing 15+ year old cars to be imported) is going to make RHD more common. So someone else may find this useful.

Issue solved for me: I'm going to use Chevron 94 octane (vancouver island ftl) Rest of the gas stations only carry 91 octane, which i'd prefer not to test quality-wise right now :p
I've also done previous research internally in these forums, and it seems a fair amount of Western-canadians are preferring Chevron as their top choice(s). Shell aswell may have been frequently listed but I've always preferred Chevron in my vehicles.

Depending on what my engine is verbally telling me, I might get her re-tuned for canadian juice.
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