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Discussion Starter #1 (Edited)
Just noticed this on Page 51 of the UK Brochure :-
The engine of the BMW M5 is designed for RON 98 fuel. Use of RON 95 or 91 fuel reduces engine output and increases fuel consumption.
Can't remember the E39 needing RON 98. Looks like it's Optimax only for top performance then.
 

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Is RON 98 the same as 98 octane by US standards? If so, I have never seen 98 octane gas outside of race fuel here in the US.
 

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greg_h said:
Is RON 98 the same as 98 octane by US standards? If so, I have never seen 98 octane gas outside of race fuel here in the US.
They are diffrent ratings. I think the translated one is ~93... Again, tough luch for CA residents... :(
 

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Discussion Starter #7 (Edited)
Gus said:
Yes - it says pretty much the same thing - power and economy optimised by using RON98..
OK, cool. I used to run my E39 on Optimax nearly all the time, but the E60 will get used much more, hence the query.
 

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The ECU is optimised to run on RON98. Putting 95 Octance fuel means the engine is not running on the idea fuel and you are compromising performance and economy.

Stick with Optimax and you can't go wrong. Most other Superunleadeds are only 97 Octane.
 

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Ashok Arora said:
The ECU is optimised to run on RON98. Putting 95 Octance fuel means the engine is not running on the idea fuel and you are compromising performance and economy.

Stick with Optimax and you can't go wrong. Most other Superunleadeds are only 97 Octane.
"only 97 octane"? best we can get in Canada is 94, why such differences between country's? weird

Rob
 

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That sucks for us in California, best around here is 91 octane. :sad3:
 

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you know, with the compression ratio of this engine, I wonder if we need to worry about more than just slightly reduced power and economy. Isn't the CR something like 12 or 12.5:1? I would be really worried about preignition, etc.
 

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See this one thing I dont understand that why in the US you cant get a good high octane fuelouich ouichwhen everything else is just perfect overthere!!!! Here in Slovakia we can buy Shell V-power 100octane!:cheers:
 

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is that 100 RON or 100 PON?

Here, found a chart...

RON MON PON
90 83 86.6
92 85 88.5
95 87 91
96 88 92
98 90 94
100 91.5 95.8
105 95 100
110 99 104.5

PON is what we are used to the US.
 

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Octane is measured differently in the US where 93us (what you get in most states) is about the same as the highest normal grades available in Europe. California is a bit of an exception, whose response to pollution issues was to impose regulations, including different gasoline grades and auto emission standards. While these do little to help the problem, it does make many feel good by making performance enthusiasts suffer.

Tom
 

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What i find funny was a test done several years ago (like mid 90s) by a car mag. They tested a standard off the shelf car right off the dealer lot against a hot rod in cherry condition and perfect running order. The FI 2.something 4 banger had higher emissions than the large V8 (seem to recall it was a 350) carbed hot rod. ouich I'll see if I can dig up the mag from the archive tonight if I still have it.
 
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