# Japanese/European Octane Vs. US/Can Octane
**URL:** https://forums.speedlife.net/t/japanese-european-octane-vs-us-can-octane/81379
**Category:** SON240sx Automotive
**Created:** [August 3, 2004, 11:43am UTC](https://forums.speedlife.net/t/japanese-european-octane-vs-us-can-octane/81379 "2004-08-03T11:43:24Z")
**Posts on this page:** 13
**Page:** 1
### Author:  [@nocwage](https://forums.speedlife.net/u/nocwage)
#### Post date: [August 3, 2004, 11:43am UTC](https://forums.speedlife.net/t/japanese-european-octane-vs-us-can-octane/81379/1 "2004-08-03T11:43:24Z")
First of.
THEY ARE MEASURED DIFFERENTLY.
Now that that’s out of the way I’ll explain why we don’t need to waste money on Sunoco 94 (and why we probably get shittier performance out of it) in our JDM motors.
European and Japanese octane rating is based on the Research Octane Test. It used unrealistic test conditions that generally give a higher rating than the alternate test method, the Motor Octane Test.
MON ratings are generally 10 below RON for the SAME fuel.
Just to confuse you, US doesn’t use MON, it uses another system called PON but it’s just an average between RON and MON.
THis is actually a superior method since poorer quality fuel could score well on RON but fail horribly at MON and vice-versa.
So what does this mean?
It means that a motor which required 95 Japanese/European Octane ACTUALLY is designed for 91 PON (US/Canada) Octane.
So this ties back to whomever it was that posted saying they got better mileage and it felt like more power out of Petro’s 91 vs. Sunoco’s 94.
As was stated in that thread (I think it was that one), higher octane in a motor that doesn’t take advantage of it (like the SR20 and CA18) will make it run WORSE since higher octane fuels are harder to burn and won’t ignite at the time and speed that the motor is expecting (since it’s expecting regular octane).
So here’s a quick chart.
RON 90 -\> PON 87
RON 92 -\> PON 89
RON 95 -\> PON 91
RON 96 -\> PON 92
RON 98 -\> PON 94
RON 100 -\> PON 96
RON 105 -\> PON 100
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### Author:  [@system](https://forums.speedlife.net/u/system)
#### Post date: [August 3, 2004, 11:51am UTC](https://forums.speedlife.net/t/japanese-european-octane-vs-us-can-octane/81379/2 "2004-08-03T11:51:11Z")
Thanks for that. I beleve that there was a lot of confusion about what gas to put in peoples cars.
I hope that this answers everyones questions.
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### Author:  [@Original\_Nutta](https://forums.speedlife.net/u/Original_Nutta)
#### Post date: [August 3, 2004, 11:56am UTC](https://forums.speedlife.net/t/japanese-european-octane-vs-us-can-octane/81379/3 "2004-08-03T11:56:08Z")
So what octane does the SR20DET use?
And what cars in Japan would use a RON 105/ PON 100?
Or even anything higher than RON 98 / PON 94?
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### Author:  [@nocwage](https://forums.speedlife.net/u/nocwage)
#### Post date: [August 3, 2004, 12:00pm UTC](https://forums.speedlife.net/t/japanese-european-octane-vs-us-can-octane/81379/4 "2004-08-03T12:00:00Z")
The CA18DET requires RON 95 so 91 regular octane.
I assume the SR20 is the same.
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### Author:  [@Jesse](https://forums.speedlife.net/u/Jesse)
#### Post date: [August 3, 2004, 8:43pm UTC](https://forums.speedlife.net/t/japanese-european-octane-vs-us-can-octane/81379/5 "2004-08-03T20:43:46Z")
get a jdm car and look inside the gascap
on 240’s it says it reccomends premium
also… do u mind if i post this info on another forum?
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### Author:  [@nocwage](https://forums.speedlife.net/u/nocwage)
#### Post date: [August 4, 2004, 6:00am UTC](https://forums.speedlife.net/t/japanese-european-octane-vs-us-can-octane/81379/6 "2004-08-04T06:00:47Z")
Why would I? 😃
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### Author:  [@DTS](https://forums.speedlife.net/u/DTS)
#### Post date: [August 4, 2004, 2:56pm UTC](https://forums.speedlife.net/t/japanese-european-octane-vs-us-can-octane/81379/7 "2004-08-04T14:56:20Z")
91 is fine in a SR if you like stock boost.
or detonation.
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### Author:  [@SHIFT\_KA24DET](https://forums.speedlife.net/u/SHIFT_KA24DET)
#### Post date: [August 4, 2004, 11:21pm UTC](https://forums.speedlife.net/t/japanese-european-octane-vs-us-can-octane/81379/8 "2004-08-04T23:21:37Z")
> [@Society Mike](#):
>
> **WRONG:
> please do NOT disemenate incorrect information on this website.
> Do your research and find out that the EPA and ISO (International Standards Office) is going around and standardizing everything, one of things that was fixed was Japanese octane measuring. They use R+M/2 just like the US and have been for a few years now.**
:owned:
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### Author:  [@jjm\_240sx](https://forums.speedlife.net/u/jjm_240sx)
#### Post date: [August 5, 2004, 3:49am UTC](https://forums.speedlife.net/t/japanese-european-octane-vs-us-can-octane/81379/9 "2004-08-05T03:49:31Z")
Also why when I put 105 race gas in my car do i Gain 30hp (proven by dino)? Is it becasue I have turboed my car? Would not get a gain in a NA car if i ran 105? (even though the SR and CA are turbo)
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### Author:  [@nocwage](https://forums.speedlife.net/u/nocwage)
#### Post date: [August 5, 2004, 5:56am UTC](https://forums.speedlife.net/t/japanese-european-octane-vs-us-can-octane/81379/10 "2004-08-05T05:56:20Z")
> [@SHIFT\_SR20DET](#):
>
> [quote=Society Mike]**WRONG:
> please do NOT disemenate incorrect information on this website.
> Do your research and find out that the EPA and ISO (International Standards Office) is going around and standardizing everything, one of things that was fixed was Japanese octane measuring. They use R+M/2 just like the US and have been for a few years now.**
:owned:[/quote]
Meh, my service manual for the 180SX/Silvia said it required 95 RON, they may have switched recently but people still go around saying you need to run 94 octane in the imported motors when really you don’t.
I wasn’t aware they had changed the rating system, but either way people are still spreading FUD about what kind of gas you need to run.
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### Author:  [@nocwage](https://forums.speedlife.net/u/nocwage)
#### Post date: [August 5, 2004, 5:59am UTC](https://forums.speedlife.net/t/japanese-european-octane-vs-us-can-octane/81379/11 "2004-08-05T05:59:39Z")
> [@jjm\_240sx](#):
>
> Also why when I put 105 race gas in my car do i Gain 30hp (proven by dino)? Is it becasue I have turboed my car? Would not get a gain in a NA car if i ran 105? (even though the SR and CA are turbo)
Higher octane gases resist detonation, if you’re running boost (OR you’ve raised compression) you’re adding pressure and heat which increase the risk of detonation.
So by running higher octane gas you’re making the combustion behave more like it would under normal conditions with regular gas.
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### Author:  [@jjm\_240sx](https://forums.speedlife.net/u/jjm_240sx)
#### Post date: [August 5, 2004, 1:59pm UTC](https://forums.speedlife.net/t/japanese-european-octane-vs-us-can-octane/81379/12 "2004-08-05T13:59:40Z")
> [@nocwage](#):
>
> [quote=jjm\_240sx]Also why when I put 105 race gas in my car do i Gain 30hp (proven by dino)? Is it becasue I have turboed my car? Would not get a gain in a NA car if i ran 105? (even though the SR and CA are turbo)
Higher octane gases resist detonation, if you’re running boost (OR you’ve raised compression) you’re adding pressure and heat which increase the risk of detonation.
So by running higher octane gas you’re making the combustion behave more like it would under normal conditions with regular gas.[/quote]
So wouldn’t that mean the higher the octane the better? I thought your point was to say higher octane then required is bad? Maybe I read it wrong…
Edit: I think your saying that your can run 91 no problem but people are saying that you need to run 94 because 91 will hurt the car? IF thats so then I see. But 94 will benefit you with more power (not to much though)
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### Author:  [@nocwage](https://forums.speedlife.net/u/nocwage)
#### Post date: [August 5, 2004, 2:29pm UTC](https://forums.speedlife.net/t/japanese-european-octane-vs-us-can-octane/81379/13 "2004-08-05T14:29:08Z")
> [@jjm\_240sx](#):
>
> So wouldn’t that mean the higher the octane the better? I thought your point was to say higher octane then required is bad? Maybe I read it wrong…
>
> Edit: I think your saying that your can run 91 no problem but people are saying that you need to run 94 because 91 will hurt the car? IF thats so then I see. But 94 will benefit you with more power (not to much though)
I said running it in an engine not designed for it, but that doesn’t mean you can’t take advantage of higher octane in a car that didn’t originally require it, advancing your timing, adding/increasing boost, raising compression are all things that would benefit by using higher octane gas (if not require it).
But yes, I was talking about people saying you HAVE to run high octane gas in the JDM motors.