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Discussion Starter #1 (Edited)
Hi all

Okay, so for the last 2 years/46000 miles, I've been using 91 octane fuel. I have a very consistent commute to gauge fuel usage. On average, driving 70+ mph, I get about 43mpg.

So, after much discussion on this board about fuel, I changed to 89 octane, the manual says so...

After 3 tank refills, wanted to "blow out" any remaining 91 fuel in tank, I started to gauge fuel usage with 89.

1. I got an immediate +4 mpg! On my last tank, it was +8!
2. It seems a little MORE responsive (phantom effect?)
3. Going from high rpm's to low quickly, there is less "blub blub" sound from engine; you know that popping backfiring sound you sometimes get

Regardless, I am absolutely getting better mileage. There is no arguing this.

Kam
 

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Let's clear something up that the owners manual shows that is confusing:

The owners manual states:
"Super unleaded, (max. 10 % ethanol, E10)
89 AKI (95 ROZ/RON)
89 AKI"


AKI means Anti Knock Index which we really don't use in the U.S, here we use (R+M)/2 method of determining octane ratings.

With this in mind if we take the European way of rating (RON) which in this case is 95 that converts over to 90-91 using our (R+M)/2 method.
So using 91 octane (Super or Premium in most states) is actually the required octane fuel rating, I have no idea why BMW lists AKI.

That does not mean that using a slightly lower octane will hurt the engine, performance or MPG though as there are several other factors that play into it.

One thing that I know for sure is that an engine is running at peak efficiency when it's on the very near verge of detonation, but to go over the edge and actually have detonation (pinging) is dangerous and can be harmful to the engine so most manufactures build and tune engines to run on a lower octane than they recommend in the manual or on the sticker near the filler neck just to be on the safe side as it's better (easier) on the engine to have too high octane gas in the tank than too low but too high octane will usually hurt performance and MPG but not the engine and that's what they have to warranty.
Another factor is elevation, the higher the elevation the lower octane fuel your engine needs.
 

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Ahh.. a question nearly as old as the combustion engine.

New to the BMWs and BMWese manual language. The one thing BMW definitely expects is that if you were smart enough to buy their product, you must be smart enough to decipher their Euro conversion to 'Merica conversion.

Been using 89 Octane since day one. Bike is only a few months old so I haven't accumulated many fuel ups yet. Riding the bike consistently like I stole it I average 43 MPG with both panniers and top case attached full time. Maybe this is the first time I've looked at this before 3am but the damn manual does say super. My confusion even led me to look at previous discussions which noted 89 mid grade. Even the other GS rider at work has a note on his wind deflector that states 89 octane. Now JetSpeed roles in here and says hey guys it's 91 octane. I even searched out the conversion online and it stated 91 Octane. Still.. with that knowledge I put 89 in the tank. Maybe I'm having a moment of clarity, or maybe its this handy recent post that says its 91. On the next fill up I'm putting 91 in.
 

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I should have added that if you are using 89 (or even lower) and the engine runs well and does not ping on it and returns good fuel economy than you are good to go.
The design of this new LC engines combustion chambers make it less prone to detonation than other engines, that and variances in fuel quality purchased at different stations are a factor.

Here is a quote about the R1200GS LC engine from a Cycle World article:
"Optimum use of intake-flow velocity to generate flame-speeding turbulence has made possible knock-free operation at this model’s higher 12.5:1 compression ratio. Fast combustion outruns the processes that lead to knock. Fuel requirement is 95 RON/91 R+M/2."

The entire article can be read here:BMW Liquid-Cools Best-Selling Boxer-Twin- Tech Preview | Cycle World

I sometimes use ethanol free 88-89 octane fuel with good results although not much improvement in MPG, maybe 1 or 2 if any.
 

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The 43 mpg is music to my ears. Just got back from a 1991 mile trip and was disappointed in my low to mid 40s mpg calculation. my '05 w/ 30k miles must be running normal and on 87. My fuel gauge gives me nervous fits. Probably 130 - 150 miles the warning message pops up. With a 5.7 gallon take I would not expect this but that is the way it is since my factory recall fuel pump event. Had this done when I bought it 2nd hand. The indicator goes from "full" to "1/3rd" in one fell swoop. I have a feeling i could easily get another 30- 40 miles before sucking "bottom" fuel.
 

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The ride of Life
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Random thoughts on this subject -

My GS seems to get about 42 MPG overall. My Hex Head RT about 4 MPG better.
I think I am putting premium in, but since the pumps have one nozzle when I request premium am I really getting that? There is bound to be some of what ever was pumped before in the hose and piping.
Here in the Repbulik of Kalaforna all of the fuel in this area seems to be E-10. That's 10% ethanol. E-85 is also available for cages with flex fuel engines.
All of my bikes seem to run just fine of regular.

- Bumblebee.
 

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Random thoughts on this subject -

I think I am putting premium in, but since the pumps have one nozzle when I request premium am I really getting that? There is bound to be some of what ever was pumped before in the hose and piping.


- Bumblebee.
This question has been asked many times and I researched it to find the actual answer some time ago and it turns out that:
The hose will have some fuel left over (whatever grade) from the person who last used the nozzle, the amount is less than .13 (about a pint) of a U.S gallon (or half a liter), so long as when you refuel you use more than 2.5 gallons the amount of residual left-over fuel in the hose is inconsequential and does not have any effect on the overall octane of the gas in your tank.
This is the reason that the Divisions of Weights and Measurement in each state have elected to allow gas suppliers to use single hose pumps to supply several differing grades of fuel.
So in a nutshell; This is nothing to be at all concerned about no matter how anal you are, the amount of contaminants on a McDonald's hamburger are a far larger worry.
 

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Discussion Starter #8
I found this...so based on the below, my USA bike should take 89 fuel. 89 aki

Anti-Knock Index (AKI) or (R+M)/2
In most countries, including Australia, New Zealand and all of those in Europe,
the "headline" octane rating shown on the pump is the RON, but in Canada, the United States, Brazil, and some other countries, the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI), and often written on pumps as (R+M)/2. It may also sometimes be called the Posted Octane Number (PON).
 

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I found this...so based on the below, my USA bike should take 89 fuel. 89 aki

Anti-Knock Index (AKI) or (R+M)/2
In most countries, including Australia, New Zealand and all of those in Europe,
the "headline" octane rating shown on the pump is the RON, but in Canada, the United States, Brazil, and some other countries, the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI), and often written on pumps as (R+M)/2. It may also sometimes be called the Posted Octane Number (PON).
If you are saying that 89 AKI is the same as 89 (R+M)/2 that is not exactly correct.

To keep this as simple as possible forget about AKI, PON and MON: BMW recommends 95 RON fuel. You can find conversion charts all over the internet that show that 95 RON is equal to 91 (R+M)/2 (but can range between 90-92 (R+M)/2) which is how it is labeled on gas pumps throughout the United States.
 

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Interesting. So lower octane should provide better fuel efficiency, as you get "closer" to pinging? Presumably that's leaving ethanol based fuels out of the comparison? I had always assumed higher octane would increase fuel efficiency!

I'm on the higher octane stuff, and generally do 60mpg, fully loaded with passenger at reasonable speeds. The flat twin seems remarkly fuel efficient to me compared to equivalent bikes I've looked at.
 

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If you're getting 60mpg avg over the course of using a full tank of gas I would not ever sell that bike or change a thing, that is the best economy I have ever heard of anyone getting with any GS.
Unless when you say; "at reasonable speeds" you mean 45mph.
 

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Discussion Starter #12
Ok, from the horses mouth...I asked bmw straight out about fuel. Here is their reply.

Dear Kam,

Thank you for contacting BMW Motorrad USA regarding fuel for your 2015 BMW R 1200 GS. We appreciate your inquiry.

BMW recommends using TOP TIER Detergent Gasoline with an octane rating of AKI 91 and alcohol content of less than 10% by volume. Only exclusive usage of TOP TIER Gasoline provides the full benefit of reducing deposits. You may find more information related to TOP TIER Gasoline on the official website: www.toptiergas.com.

If you choose to use less than 91 AKI, please note we do not recommend fuel with an octane rating below 87 AKI. Our BMW engines are equipped with knock sensors and will adapt automatically to different octane ratings, provided the minimum octane requirement is met. Fuels with higher octane ratings will provide enhanced performance with lower fuel consumption; however, fuels with lower octane ratings will have the opposite effect.

For your convenience, the BMW Motorrad Customer Relations and Services Department is available Monday through Thursday from 9:00 a.m. to 9:00 p.m. ET and Friday from 9:00 a.m. to 6:00 p.m. ET. You can reach us at 1-800-831-1117.

Thank you again for taking the time to write to us.

Regards,

Katie Sullivan
BMW Motorrad USA
Representative

MAKE LIFE A RIDE.

FEEL EVERYTHING, FEAR NOTHING.
Build your own bike at www.bmwmotorcycles.com.
 

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If you're getting 60mpg avg over the course of using a full tank of gas I would not ever sell that bike or change a thing, that is the best economy I have ever heard of anyone getting with any GS.
Unless when you say; "at reasonable speeds" you mean 45mph.
On mountain roads at enjoyable speeds, or doing 70-80 fully loaded, strangely no matter what I seem to do I achieve that figure roughly... Fully loaded with passenger. Solo easy going riding knocks it up to 70+. It's a French bike... Running on French "98" octane fuel. Could that explain it ? Figures seem quite normal in France on other LC bikes, although I'm probably on the low side overall. No city driving, and I don't race, but I don't drive slowly either...


Sent from my LG-H815 using Tapatalk
 

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Well Kam, Katie Sullivan doesn't know her ass from her elbow.

The new liquid cooled GS motors do not have knock sensors for one, and if they did that would allow for the use of lower octane fuel without worry about engine damage not the other way around.

She used the term AKI even though she is with BMW USA and in the U.S we don't use AKI we use (R+M)/2 octane ratings on the pump.

The blanket statement that: "Fuels with higher octane ratings will provide enhanced performance with lower fuel consumption; however, fuels with lower octane ratings will have the opposite effect." is not necessarily true and many GS riders would sign legal documentation certifying such, me included.

The part about the Top Tier gasoline is mostly true but irrelevant to octane and you can buy non top tier fuel and add a dose of Techron to essentially make your own top tier fuel, I do this on occasion.
 

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Discussion Starter #15
Well Kam, Katie Sullivan doesn't know her ass from her elbow.

The new liquid cooled GS motors do not have knock sensors for one, and if they did that would allow for the use of lower octane fuel without worry about engine damage not the other way around.

She used the term AKI even though she is with BMW USA and in the U.S we don't use AKI we use (R+M)/2 octane ratings on the pump.

The blanket statement that: "Fuels with higher octane ratings will provide enhanced performance with lower fuel consumption; however, fuels with lower octane ratings will have the opposite effect." is not necessarily true and many GS riders would sign legal documentation certifying such, me included.

The part about the Top Tier gasoline is mostly true but irrelevant to octane and you can buy non top tier fuel and add a dose of Techron to essentially make your own top tier fuel, I do this on occasion.

hahahahahahahah! and the plot thickens!

- one point that I did find, that the "internet" does state that in the USA, our meaning of AKI is (R+M)/2
- I am one of the people that will state that I DO get better mileage from 89 than 91
- I've heard [from this group] that the bike does not have a knock sensor, so I cannot comment on her comment!

After really looking at the manual, applying Sherlock Holmes level staring at it, I've come to the following thoughts --

They state that the "Recommended fuel quality" (for the USA as this is a USA bike) and it means that the following are ALL good, is --

#1. Super Unleaded, being 91 AKI in the USA (AKI means the (R+M)/2)
#2. 89 AKI (95 ROZ/RON)
#3. 89 AKI

Then they state you could use the "alt" fuel...

I'm sticking with 89 unless someone says otherwise!

~Kam
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`

here are some charts I located, just for a FYI for everyone...
from : Octane rating conversions - PencilGeek's BMW Blog

Actual octane rating table

EURO RON MON US: (R+M)/2
90 83 86.5
92 85 88.5
95 87 91
96 88 92
98 90 94
100 91.5 95.75
105 95 100
110 99 104.5


Formula for converting EURO to US rating
I've also come up with a pretty good formula that approximates US octane rating based on EURO RON rating, and visa versa. The formula is US=RON*(21/22):

EURO RON US (R+M)/2
90 85.9
92 87.8
95 90.7
96 91.6
98 93.5
100 95.5
105 100.2
110 105


Formula for converting US to EURO octane
And reversing that forumula, wet get: RON = US*(22/21)

US (R+M)/2 EURO RON
87 91.1
88 92.2
89 93.2
90 94.3
91 95.3
92 96.4
93 97.4
94 98.5
95 99.5
96 100.6
97 101.6
98 102.7
99 103.7
100 104.8
 

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I don't get why you can't comment on her bogus comment or why you keep insisting that AKI is the same as (R+M)/2 in the U.S when the charts that you posted clearly say otherwise.

89 AKI = 91 (R+M)/2
 

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Discussion Starter #17
I don't get why you can't comment on her bogus comment or why you keep insisting that AKI is the same as (R+M)/2 in the U.S when the charts that you posted clearly say otherwise.

89 AKI = 91 (R+M)/2
I don't get why you can't comment on her bogus comment or why you keep insisting that AKI is the same as (R+M)/2 in the U.S when the charts that you posted clearly say otherwise.

89 AKI = 91 (R+M)/2
Wow jetspeed, why the anger?

I cannot comment on her comment about the knock sensor, as I don't know if she is right or wrong. I have no idea if the bike has one or not.

My understanding is that in the USA, the term AKI is the same as the (r+m)/2. That's my understanding.

The charts don't use r+m/2, they use 21/22 for the factor.

Again, just posting charts that others may want to see.

I don't understand what you mean by

89 AKI = 91 (R+M)/2

Kam
 

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I've gone to Mexico a couple of times and put Mexican gas in, PEMEX, only two grades available, Magna (regular) and Magna Premium, no mention of octane...bike runs great. Seems better than the US gas. Looking at the internet it appears to be 86 octane, now what rating method they use I don't know.

I know there will be people who disagree, but somehow I don't think it matters all that much.

So, hmm.
 

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Discussion Starter #19
We should ask the question backwards, what gas didn't work?!

I mean not like "bad" gas, but ratings.

This is actually a very informative thread. All these new terms! RON, MON, ROZ, TKI...
 

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No anger in the least, not even a little bit.

What I mean by "89 AKI = 91 (R+M)/2" is exactly what is written. Fuel having a rating of 89 AKI has a rating of 91 if converted to (R+M)/2, these two octane ratings are close but not exactly the same.

And I can guarantee you (as others can as well) that the liquid cooled engine in your 2015 does not have knock sensors, they are not needed due to the combustion chamber and intake/exhaust port design, the previous model hex and cam head engines did have knock sensors.

The gal from BMW is copy and pasting from an old canned response form, she knows less about these bikes than Pee-wee Herman.

In the end none of this matters much anyhow due to the fact that people are running everything from 85 to 100 octane race gas in their GS's and I have yet to hear of a motor blowing up becasue of it.
 
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