Octane Question

Is anyone using low octane fuel in their wetheads? I was riding with someone last week who only uses low octane in his K1200. I know it's a different engine but I wondered if anyone ever gave it a try on their new wethead.

The manual calls for 89 AKI. If you can't find 89 it wont hurt to use 87 once in awhile.
The manual say if you use 87 AKI all the time the bike needs to be reprogrammed.

collesidis said:

Is anyone using low octane fuel in their wetheads? I was riding with someone last week who only uses low octane in his K1200. I know it's a different engine but I wondered if anyone ever gave it a try on their new wethead.

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https://plus.google.com/+JohnSherman2/posts/AmHm7Qj4rk6

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I use low octane fuel during winter cold months but when I do I don't run engine RPMs higher than 4.5k. Summer higher octane then I will take RPMs to rev limiter stop. Just my theory for my 2016 R1200RT wet head.

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Higher octane will yield better gas mileage, so in my book it's almost a wash and certainly not worth possibly damaging a very expensive engine. Pay for the high octane if it's available.

dabubba said:

Higher octane will yield better gas mileage, so in my book it's almost a wash and certainly not worth possibly damaging a very expensive engine. Pay for the high octane if it's available.

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My Hexhead has knock sensors so I'm not worried about engine damage. Using low octane does slightly lower gas mileage and power, noticeably reducing my passing acceleration. The price difference is not significant in the grand scheme of things, so I use premium exclusively and enjoy the power - that's a part of why I bought the bike.

I assume the Wethead has some sort of knock management system, but have not heard any description of how it might work. I understand the knock sensor has been eliminated, so without knowing IF the bike is protected against pre-ignition, I'd play it safe and use the specified fuel.

johnesherman said:

I use low octane fuel during winter cold months but when I do I don't run engine RPMs higher than 4.5k. Summer higher octane then I will take RPMs to rev limiter stop. Just my theory for my 2016 R1200RT wet head.

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Can you explain your thinking in that decision, as it really makes no sense to me.
The danger of lower octane fuel is pre-ignition, or knocking. Most likely to occur at lower revs (not higher), in hotter temps (not winter), and under higher load (carrying mucho weight or ascending serious grades.

Well, answer to your question: octane, RPM, & winter, my theory applied. No high RPMs with lower octane fuel used during cold winter riding.

See generally,

https://www.hemmings.com/blog/2014/...the-fiction-behind-those-higher-priced-fuels/

http://www.faqs.org/faqs/autos/gasoline-faq/part3/section-1.html

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dabubba said:

Higher octane will yield better gas mileage, so in my book it's almost a wash and certainly not worth possibly damaging a very expensive engine. Pay for the high octane if it's available.

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The question is higher than what? My GS is rated for 89 aki. You might get some knock using 87 but you do NOT get better mileage or anything else from going to 92. The BMW engineers built the engine for 89 and state you can use 87 in a pinch. 92 was never in the game. If you want better mileage get non-alcohol, straight, old fashioned gas rated at 89.

johnesherman said:

Well, answer to your question: octane, RPM, & winter, my theory applied. No high RPMs with lower octane fuel used during cold winter riding.

See generally,

https://www.hemmings.com/blog/2014/...the-fiction-behind-those-higher-priced-fuels/

http://www.faqs.org/faqs/autos/gasoline-faq/part3/section-1.html

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still leaves me asking that proverbial question "why bother with either limitation- lowered rpm and/or lower octane? to save a few pennies? I know on my '16GS, keeping it under any arbitrary rpm (other than redline) is not an easy task... and certainly not when it's just getting into the fun zone of above 5K.

i guess that's why they make bagels, ice cream, pie, donuts and pizza in all kinds of flavors... to each his own.

bikerfish1100 said:

still leaves me asking that proverbial question "why bother with either limitation- lowered rpm and/or lower octane? to save a few pennies? I know on my '16GS, keeping it under any arbitrary rpm (other than redline) is not an easy task... and certainly not when it's just getting into the fun zone of above 5K.

i guess that's why they make bagels, ice cream, pie, donuts and pizza in all kinds of flavors... to each his own.

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The simple answer: Use the BNW OEM suggested octane fuel minimum rating for entire RPMs use and enjoy the ride [emoji4]

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I was taught many years ago that you should use the lowest octane gas that the engine will not pre-detonate with. This would provide the best fuel economy. This was before knock detectors, ECU's, fuel injection, etc. I was able to find the following to support this.

"Use the recommended gas for your car. Going lower than the recommended may reduce fuel economy as the engine may have to retard timing to avoid detonation. Going higher than recommended won't help as your engine is unable to take full advantage of it, as well as the fact that higher octane fuels actually contain slightly less energy (they just offer a more controlled burn that higher compression engines can take advantage of)."

Even more information.

http://www.fueleconomy.gov/feg/octane.shtml

dabubba said:

Higher octane will yield better gas mileage, so in my book it's almost a wash and certainly not worth possibly damaging a very expensive engine. Pay for the high octane if it's available.

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This is not true and has been proven study after study. Google is your friend....If it were true every single car manufacturer would call for super unleaded in every car to help epa mpg requirements.

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BMARC153920 said:

This is not true and has been proven study after study. Google is your friend....If it were true every single car manufacturer would call for super unleaded in every car to help epa mpg requirements.

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This needs some clarification. Using higher than specified octane does not improve mileage. But for some engines with high compression ratios like the R1200 in question here, using the specified higher octane DOES improve mileage, because that is the fuel the engine is designed to burn. Using lower than specified octane can produce knock, causing the ECU to change spark timing, reducing power and efficiency.

LFarling said:

My 2015 LC RT calls for 93. Not sure where all these other numbers come from but 93 is what my bike runs.

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According to the rider's manuals posted on the BMW Motorrad site, 89 AKI is specified for that model.

LFarling said:

My 2015 LC RT calls for 93. Not sure where all these other numbers come from but 93 is what my bike runs.

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I have a 2015 GSA, and the recommended fuel is super unleaded 89 AKI. Sure you've got that right, as we've got the same motor? In fact the sales guy took pains to point that out when I took delivery, since the recommended fuel grade for my 2006 RT that I traded in was 91.

Are you looking at the RON -- and not AKI -- number?

Manual page for fuel recommendation

Here's a scan of manual. US version

Here's an excerpt from this website: http://www.repairfaq.org/filipg/AUTO/F_Gasoline6.html#GASOLINE_001


Learn something new every day. I always used 93 when I could get it figuring better power and fuel economy. I'll start using 89 from now on.

marcopolo said:

... Are you looking at the RON -- and not AKI -- number?

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I'm sure that's exactly what's being done Marc. The manual specifies 93 RON for some BMW engines (European rating - an older system with flaws) which is 89 AKI (North American rating - a better method of classification). I have never seen any volume produced car or motorcycle in NA specify 93-AKI. The RTW calls for 95-RON which is 91-AKI.

This is starting to look too much like a bad oil thread.

Please remember, a little knowledge can be a dangerous thing, and, just because someone else said something or wrote something on the internet does not make it so. Also, do not think that what applies to generalized statements cars can blindly be applied to the specific requirements of motorcycle engines.

Unfortunately, far too many folks with too little depth of understanding on these matters are willing to provide pearls of wisdom and confuse matters significantly.

First, without sufficient information from BMW engineers or running detailed tests on these specific engines, we can only go by what information we do have from BMW and what is KNOWN about octane and engine management.

So, let us look at what BMW has published. BMW specifies that their maximum HP rating for the R1200RTW is achieved using 95-RON which is 91-AKI and that is the fuel they suggest. If we were talking about the previous generation 1200 (1170cc) engine, than things are different. IN that situation BMW provide two RON grades 95 and 98 (AKI 89 and 91) and identify that maximum HP is obtained using 91 AKI (98-RON).

That absolutely does not mean that the R1200RTW will produce any more or less HP with anything higher than 91-AKI. In fact it would indicate (not state, but indicate) that there would be no gain, otherwise, BMW would have followed their existing practice of identifying this.


Will the R1200RTW run on 89-AKI? Yes.

However, it will not run as optimally designed. The ability to operated in an acceptable manner on 89-AKI is a compromise due to poor fuel quality standards in the US and elsewhere. For some markets BMW used to specifically de-tune engines ECU (different mapping, part #, etc.) so they'd run on the typically inferior quality gas prevalent in those areas.


Will doing so provide any benefit whatsoever? Unlikely and you may reduce your long-term relaibiliy if you keep the bike.

The 3% (approx) cost savings between the two grades of fuel has as much or more to do with the differences in the "Additive Package" to the different fuel grades as it does with the octane difference. So, even if the lost of fuel economy by running 89-AKI is say 2% (I don't know the actual figure, but do know that it will exist) than there is a 1% savings in cost per mile ridden for the fuel expenditure, but, through that running/savings there has been an inferior additive package being used that in most cases is not as effective at reducing/ removing carbon deposits, gunk and wear. For instance, Shell's 91-AKI, V-Power NiTRO+ Premium Gasoline (which I use when practicle), "removes an average of 60% of performance-robbing gunk on intake valves left behind by lower quality premium gasolines".

Does a higher compression ratio require a higher octane fuel? No, not necessarily. The better the combustion chamber design is the lower octane it can run without any lose of power, fuel-economy, etc. I have seen engines with CRs of 9:1 that required 91-AKI to avoid detonation and others like my R1200RTW that have a 12:1 CR and are optimized to run on 91-AKI. It is a matter of design, and can not be blindly referenced from unrelated writings about any other engine.

As an aside, one of the reasons I run Shell V-Power is that indepentently of each other, I have had two top motorcycle engine builders (multiple National Championship winning) tell me that they tuned street bikes using Shell V-Power exclusively as they found their motorcycle engines made 1-2 HP consistantly using it vs any other readily available pump gas. YMMV

Just so you know, whenever I buy a vehicle from someone, I casually ask them what fuel the vehicle takes. If they admit that they run a below spec grade, I automatically reduce my maxium I'm willing to pay for it due to the "possibility" of issues. It isn't worth the possible 1% fuel cost saving only to end up with a top-end valve job perhaps 10% sooner - that is far more expensive. Would that happen? I don't know anymore than much of the unfounded speculation that has been posted here on the benefits running a "permissible but below recommended" octane for extended periods of time in this specific engine.

I do know that there is far more difference between Top-tier 91-AKI and 89-AKI than just the octane rating and not taking that into consideration has it's own costs. For me, I run what the manual states. Now oil is a different beast, anyone want to go down that worm-hole?

^ I like this guy

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