Sport Bikes banner

1 - 18 of 18 Posts

·
Registered
Joined
·
1 Posts
Discussion Starter · #1 ·
Hey guys, I was wondering: My bike isn't firing up at the moment and I was wondering if it's because I've been putting 87 when the bike needs 91 octane. Any information is appreciated.
 

·
Registered
Joined
·
4,689 Posts
I write something like this up every couple of years. Now is as good a time as any.

The manufacturer tells you what it's tuned for. If your bike is in proper repair, then:

1: Running higher octane will give you, if anything, worse mileage and performance, as a higher octane rating means the fuel is harder to ignite (reduces preignition / knock) and the components that raise the "octane rating" have less energy stored within them.

2: Running lower octane may be OK, or may not be OK. You'll have to watch it. Not recommended when a vehicle is under warranty or if you thrash it about. Many vehicles have sensors and will retard timing (reducing mpg and performance) if the gas is too low.

Keep in mind, that there are 2 different rating systems for "octane" and in the US we use the average of the 2 and call it "anti knock index" - this is what is meant by the (R+M)/2 you often see. In Europe, they use only the "R" number...which is higher...leading many people to believe they europe gets "better gas". Not only is higher not necessarily better (as above)...but an "R" octane rating of 91 (euro style) is pretty much the same as our 87. That said, it is generally easier over there to get "98" which could be the equivalent of 94 here.
 

·
Registered
Joined
·
743 Posts
The only way low octane fuel could keep your bike from starting would be if it had partially destroyed the plugs with predetonation.
 

·
You are here
Joined
·
3,535 Posts
I really don't think it matters that much. I tend to put premium in mine just because the gas around here sucks. I put regular in it for years and it did nothing but run.
 

·
Registered
Joined
·
4,689 Posts
OK, that's it. Time for us to send Piers back.

Just kidding. We hit that point long ago. :\
 

·
Registered
Joined
·
357 Posts
See the 'battery' thread on this page. If one cell goes bad on those crap lead-acid batteries then you have 10v instead of 12v which still allows the starter to turn over but drops the voltage going to the plugs. If the battery is more than 3 years old then toss it. Gasoline octane has nothing to do with starting; it is required to prevent combustion pre-ignition and detonation under engine load.
 

·
Registered
Joined
·
4,689 Posts
The funny thing is n-Octane, which is what one would generally assume when they hear "octane"....an 8 carbon atom chain....would actually have a very, very low "octane" rating (somewhere under 20) - it would burn/detonate way too easily.

When people speak of a high octane rating in gasoline, they're generally referring to iso-octane - meaning a "different shape" of 8 carbons....specifically, 2,2,4-trimethylpentane. This has an "octane rating" of 100.
 

·
Registered
Joined
·
62 Posts
The funny thing is n-Octane, which is what one would generally assume when they hear "octane"....an 8 carbon atom chain....would actually have a very, very low "octane" rating (somewhere under 20) - it would burn/detonate way too easily.

When people speak of a high octane rating in gasoline, they're generally referring to iso-octane - meaning a "different shape" of 8 carbons....specifically, 2,2,4-trimethylpentane. This has an "octane rating" of 100.
Okay.:shrug
 
1 - 18 of 18 Posts
Top