Gas octane at higher elevations

[TJ]

Just learned that you can use a lower octane at higher elevations. Since we just moved to Peyton CO which is approximately 6,200 feet I am wondering if 85 or 85.5 octane is safe to use in our bikes?

[Rick Hall]

At elevation, lower your octane requirement by two.

Up here, 85 octane is 'regular' grade, the same as 87 octane at sea level.

Rick

[maxtog]

If I remember correctly- the higher the octane, the slower the burn and/or more retarded the ignition is.  Higher performance engines, especially with higher temps and compression, need a higher octane to prevent preignition of the fuel.  Higher octane fuel is actually less energetic and should only be used when required by the engine design.

At higher elevations, there is less pressure and less oxygen per unit of air.  That will retard the ignition and slow the burn with less need for more octane.

[Rhino]

Hello TJ, welcome to my neck of the woods. I live in the Black Forest area. Our bikes call for 90 octane at sea level. You can definitely get by with less at higher altitude due to what Maxtog said. Typically in this area regular is 85, Mid Grade is 87 and Premium is 89. You can use 87 without any knocking but not sure about 85. I use premium only because there are times I have been traveling and could only find 85. If I'm half full with 89 and put some 85 in I think I end up with 87. Better then pure 85.

[aspire61]

Interesting. Even though i have only had my bike since last fall, i have always filled up with regular. I will consider high octane once the weather warms up to summer highs. I have never actually considered elevation as part of the equation, only ambient temps and city driving.

Wouldn't the ECS compensate for lower air flow, thus injecting a slightly smaller volume of fuel?

chrs- mat

[Rhino]

Altitude is definitely part of the equation. Octane effects the flash point of the gas and higher octane is used in higher compression engines so there is no pre-detonation aka knocking. Less atmospheric pressure means less actual air getting into the cylinder less compression, lower temps in the combustion chamber means lower flashpoint gas can be used.

[TJ]

Hello TJ, welcome to my neck of the woods. I live in the Black Forest area. Our bikes call for 90 octane at sea level. You can definitely get by with less at higher altitude due to what Maxtog said. Typically in this area regular is 85, Mid Grade is 87 and Premium is 89. You can use 87 without any knocking but not sure about 85. I use premium only because there are times I have been traveling and could only find 85. If I'm half full with 89 and put some 85 in I think I end up with 87. Better then pure 85.

Thanks. I was thinking we only needed 87 at sea level. But since my bike and manual are still with the movers I could easily be wrong. Hope to have her on the road by 13 May. I am soooooo looking forward to riding again after a short, cold, season last year.

[maxtog]

Thanks. I was thinking we only needed 87 at sea level. But since my bike and manual are still with the movers I could easily be wrong. Hope to have her on the road by 13 May. I am soooooo looking forward to riding again after a short, cold, season last year.

The bike clearly calls for 90 octane [at sea level, although that is not said] both in the operator's manual and the sticker on the gas tank (which of course I and most people remove).  87 is not high enough.

Quote:

"NOTICE: Use minimum of 90 octane gasoline only to prevent severe engine damage."
"NOTICE: Never use gasoline with an octane rating lower than the minimum specified by Kawasaki."
"NOTICE: Avoid using blends of unleaded gasoline and methanol (wood alcohol) whenever possible, and never use “gasohol” containing more than 5% methanol."
"Use clean, fresh unleaded gasoline with a minimum Antiknock Index of 90."
"Operating problems that result from the use of poor quality or non-recommended fuel may not be covered under your warranty."

[gPink]

Alky is all but unavoidable and it's all E10 as far as I know. Til fedgov decides E15 is better for us that is.

Max is that 90 a RON number?

[maxtog]

Alky is all but unavoidable and it's all E10 as far as I know. Til fedgov decides E15 is better for us that is.

Max is that 90 a RON number?

It is E10 here also (stupid idiots).  Anyway, quote:

"The Antiknock Index is an average of the Research Octane Number (RON) and the Motor Octane Number (MON) as shown in the table.

Octane Rating Method         Minimum  Rating
================       ============
Antiknock  (RON + MON)               
Index         ---------------                 90
                          2                                                       "

[daveyboy]

I was really surprised that this bike calls for 90 octane--its compression ratio is lower than many other bikes that only require regular.

[maxtog]

I was really surprised that this bike calls for 90 octane--its compression ratio is lower than many other bikes that only require regular.

Normal compression ratio is a major factor, but not the only factor.

We have to trust that Kawasaki engineers are competent at choosing the correct octane specifications.  Unnecessarily high octane lowers mileage and performance- neither is something they would want to do.

[Son of Pappy]

I was really surprised that this bike calls for 90 octane--its compression ratio is lower than many other bikes that only require regular.

Variable Valve Timing.  Compression goes up as RPMs increase.

[Pokey]

Never less than 89 for me......Never less!!!!!

[VirginiaJim]

Really?  You know, this is strange, I was riding back from South Hill, VA today and I was thinking that we hadn't had an octane thread in a quite bit of time.  I must be psychotic.

[gPink]

...or psychedelic.

[CRocker]

Really?  You know, this is strange, I was riding back from South Hill, VA today and I was thinking that we hadn't had an octane thread in a quite bit of time.  I must be psychotic.

Yeah...

[Conrad]

Really?  You know, this is strange, I was riding back from South Hill, VA today and I was thinking that we hadn't had an octane thread in a quite bit of time.  I must be psychotic.

 

[bluedogok]

Alky is all but unavoidable and it's all E10 as far as I know. Til fedgov decides E15 is better for us that is.

Max is that 90 a RON number?

You can still find E0 in places away from the major metros with EPA issues. A gas station not too far from my parents in Oklahoma City has both E0 and E10.