Octane ratings- on the road

[OH Bob]

Hi Gang!

 

Just returned from the Canadian Atlantic Provinces and made an amazing discovery regarding Octane requirements for my 01' R1100RT! While touring Newfoundland I had to make several fuel purchases from somewhat spartan stations, i.e. a single gas pump on a gravel driveway. Much to my suprise, the bike ran just fine on 87 octane fuel. The air temps ran from the high 60's to the high 80's, and the motor ran with no apparent problems- no pinging or loss of power.

 

Have I been duped into running Premium fuel in the U.S. when it's not really required, or is it just that in the short-run lower octane fuel has no ill effects?

[Paul Mihalka]

The official recomendation by BMW is 89 octane or mid-range. As in most things like that, there is a substantial safety margin built into that. I would expect that most bikes most of the time can run on 87 octane without any ill effects.

[KDeline]

I'll say again, I have allways run the cheapest gas I can find and have never had a problem.

[smiller]

The 1100's seem to do fine on regular fuel. Note that they raised the compression ratio slightly in the 1150 and again in the 1200 though so they may be more picky.

[Paul Mihalka]

The R1200 family of bikes have a knock sensor so you can't really hurt them with lower octane gas.

[Rottweiler]

A knock sensor will retard the timing to prevent knocking but the engine must knock a little for the sensor to detect knocking first. Therefore the engine will still knock a small amount if your engine is prone to that with lower octane fuels. Over many years of riding this small amount of knocking could potentially cause damage. Also with the engine timing retarded, engine performance will be somewhat decreased. While many engines will run fine on regular gas, if you detect any knocking AT ALL you should switch to mid grade (or higher). The knock sensor is there as a safety stop much like the rev limiter, but it shouldn't be used all the time.

[Global_Rider]

While touring Newfoundland I had to make several fuel purchases...the bike ran just fine on 87 octane fuel.

 

Well Newfoundland, at least the west coast is as flat as Florida.

 

If you're not loading the engine, you won't need high octane fuels. Mountain roads, pulling a trailer, high speeds and high temperatures have a higher octane requirement.

 

I ran Shell V Power 100 in the Alps. Lots of low RPM switchbacks and steep grades along with very high temperatures made me spend the extra Euros.

 

Any chance of a tour report with PICS?

[smiller]

The R1200 family of bikes have a knock sensor so you can't really hurt them with lower octane gas.

Quite right, I forgot. Corrected by a salesman!

[smiller]

A knock sensor will retard the timing to prevent knocking but the engine must knock a little for the sensor to detect knocking first. Therefore the engine will still knock a small amount if your engine is prone to that with lower octane fuels. Over many years of riding this small amount of knocking could potentially cause damage. Also with the engine timing retarded, engine performance will be somewhat decreased. While many engines will run fine on regular gas, if you detect any knocking AT ALL you should switch to mid grade (or higher). The knock sensor is there as a safety stop much like the rev limiter, but it shouldn't be used all the time.

An occasional and slight amount of knocking usually won't hurt an engine at all, and certainly not the minute amount required to trigger most knock sensors. Certainly it is a good idea to run a high enough octane so that you won't be into the knock sensor all the time, but even if you are I doubt there would me any measurable detrimental effect on the engine.

[4wheeldog]

R11xx bikes do not have any form of knock sensor.

[smiller]

R11xx bikes do not have any form of knock sensor.

 

I don't recall anyone saying that they did.

[teecro]

R11xx bikes do not have any form of knock sensor.

 

I don't recall anyone saying that they did.

Nope they do not but Paul went and confused everyone bring up the R1200.

 

Typical Salesman trying to confuse things

[Paul Mihalka]

The 1100's seem to do fine on regular fuel. Note that they raised the compression ratio slightly in the 1150 and again in the 1200 though so they may be more picky.

This is why I brought up the R1200 bikes. Now go pick on your used car salesman - Any used car salesmen among us? -