Quote:
Originally Posted by hybris4u
Do you guys know if the octane is the "same" between different countries? Or does the way we measure differ between countries?
I drive mine on 98 octane as that is the most common in Sweden. It would be ok to use 95 octane but the price difference is to little to not always run it on 98 octane. Not sure if they sell 100 octane any more over here.
But would 98 octane in Sweden also be 98 octane in the US? Sorry if this is a stupid question but I just assume there is some difference... ;-)
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If I made a mistake in the following, please correct me.
I'll try my best.
Octane rating is derived differently in the US vs. how it is derived in the UK, Europe, S. Africa, and Australia.
There are 2 main tests used to detect the octane rating of a fuel.
There are RON and MON.
RON is "research octane number". It is used in the UK, Europe, S. Africa,
and Australia.
MON is "motor octane number".
PON is "pump" octane number". It is derived by the (R+M)/2 method. So, it's an average of both test methods.
It is used in N. America.
On average, MON results in an 8-10 point lower octane number.
PON results in a 4-5 point lower octane number.
Using that info a PON of 91-AKI (anti knock index) rating in N.America would be about 95-96 RON rating outside of N.America.
A PON of 93 rating would be about 97-98 RON in Europe and Australia.
Both RON and MON methods use a variable compression ratio engine.
RON uses a lower rpm, around 600rpm, to run it's test.
MON uses a higher rpm, around 900rpm, variable ignition timing, and
pre-heated fuel in order to create a higher stress load on the engine.
In terms of testing method, MON seems to be a better indicator of how the fuel responds as the test method tries to better mimic daily driving conditions.
Many people say that US gasoline is of lower quality, but I think that's the result of many people not understanding the rating system. From that, people have assumed that RON's larger numbers are thus "better" than the number we see in the US and N. America. However, once you know how the numbers are derived, you then know that N. American gasoline is just as good as Euro gas in terms of octane rating.
There are some factors, like sulfur content and the use of ethanol, in US gas and diesel fuels that contribute to a perception of "inferior" US and
N.American fuels. Euro regs are stricter on sulfur content especially in diesel. But, US fuel production is getting stricter as well.
It costs more money to produce ultra low to 0 sulfur fuel and that's one reason Euro fuels are more expensive.
As for ethanol, 10% formulations are the norm in the N. American market. By 2010 nearly all US gasoline is E10, or 10% ethanol. There are some limited markets that have less, down to 0 ethanol.
Many Euro markets have E5-5% formulations, with E10 becoming more common. Australia has E10 available as well.
Ethanol has a lower thermal content and thus lower MPG per volume, but it's also a high octane fuel, and it's used to help increase octane rating.
Edit: added some corrections