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Posted by: davidcalvin Sep 4 2004, 04:58 PM

Earlier I started a thread on gas. What kind should I put in my tank?

Everyone basically said, 87 is what you need. I just got my 914 and I was out and bought some gas today. And I dutifully chose 87.

While I was pumping my gas, though, I looked down and there I saw a decal, in german, which read to the effect of "minimum 91 octane".

So what gives? Which is better? 87 or 91?

Thanks,

david

Posted by: TimT Sep 4 2004, 06:21 PM

the octane rating you see at the pump is an average of two octane ratings

I believe R and M over 2= research octane over motor octane...

Im to lazy now to look it all up again..

Unless you have a high compression engine.. there is no need for the higher octane.

Posted by: Elliot Cannon Sep 4 2004, 06:25 PM

Try 87. If the engine don't like it, go to 91. Simple.

Cheers, Elliot

Posted by: lapuwali Sep 4 2004, 06:34 PM

The German label specifies 91 ROZ (aka RON, or Research Octane Number, one way to measure octane). The US system is to average RON and MON (Motor Octane Number) to get pump octane. MON is typically 8-12 numbers lower than RON (varies based on exact fuel chemsitry), so RON is always higher than US pump octane. 91 RON is roughly equivalent to US 86 octane, so using 87 by the US measure is fine. European "premium" is typically 98 RON, or about 92 by the US measure.

btw, early 1.7s required higher than 91 RON even stock, and I have to run my '71 1.7 on premium or it pings. They had higher compression than the later engines. I think the 1.8 had the lowest compression, and the lowest octane requirement.

Posted by: SirAndy Sep 5 2004, 12:45 PM

lapuwali is right.

european specifications are different and don't translate into US octane ratings ...
Andy

Posted by: ChrisReale Sep 5 2004, 09:05 PM

Ok. One last time.

I have 8:1 compression ratio. What USA octane do I need? None of this Ron, MOn shit. Say it and say it loud...

Posted by: SirAndy Sep 5 2004, 09:39 PM

start with 89 and listen to your engine. if it "knocks", go to 91, if not, call it a day and be happy with it ...

altough, 8:1 is kind of unusual. are you sure about that?
Andy

Posted by: ChrisReale Sep 6 2004, 01:00 AM

Euro pistons are 8:1, right? Nothing seems unusual about that

Posted by: SirAndy Sep 6 2004, 01:06 AM

oops, you're right, 8.0:1 for a 2.0L, 8.2:1 for a 1.7L and 8.6:1 for a 1.8L ...

my bad,
Andy