Gas Octane

[Steveyacht]

I have been using 91 to 93 octane gas since I bought my RT. Is it ok to use midgrade, ie: 89 octane?  Not that I'm cheap, but if there is no upside to use the more expensive gas, sometimes $.40 per gallon more than 89 octane, why should I?  That or am I just being too frugal?

 

Thanks in advance, 

 

S

[wbw6cos]

Yes, you are being too frugal.    The cheapest thing on  BMW motorcycle...........is 

Spoiler

the NUT in the seat!!!   

 

 

I alternate between mid and high.   Mostly mid grade twice per 1 high octane.   I commute with the bike every other week.   When on rides in the twisties, I have to take what I can get.   That translates to filling up with the good stuff prior to leaving out.    

 

No performance issues so far.   

 

Your miles kilometers may vary.

 

 

[Daveyator]

The only thing you might see is slightly less mileage and/or power. Won’t hurt your engine. I think it’s well know that premium gas and gas grades in general have always been a way to get us to pay more for gas but is only absolutely required in very few engines.

[Twisties]

IIUC, the bike has a knock sensor and will retard performance to eliminate knocking.  Consequently, you would not damage the engine, but you might not have full performance.  Probably not an issue in commuting or city driving.  You might prefer premium for canyon carving.  I don't believe fuel economy would be adversely affected.  If, as I understand it, the energy content isn't any different, just the resistance to knocking varies between the grades.  In fact, it might go up since the engine might be running in a more conservative manner.  

[TSConver]

1 hour ago, Twisties said:

IIUC, the bike has a knock sensor and will retard performance to eliminate knocking.  Consequently, you would not damage the engine, but you might not have full performance.  Probably not an issue in commuting or city driving.  You might prefer premium for canyon carving.  I don't believe fuel economy would be adversely affected.  If, as I understand it, the energy content isn't any different, just the resistance to knocking varies between the grades.  In fact, it might go up since the engine might be running in a more conservative manner.  

 

The 1250s have knock sensors, the 1200 WC motors do not.

[Bill Murray]

From my research on the Internet (so we know it must be right ), BMW recommends we use 95 octane RON (which is the primary European octane standard). The 95 octane RON is equivalent to 91 octane standard used in the United States (MON/PON). 

 

Personally, I always use "premium" grade, which is usually a 91 or 93 octane. I prefer to hedge a little on the wholesale quality of whatever distributor is filling up a station's tanks. Most mid-grades in my area are 89 octane. Probably what is just as important, if not more important, is the "quality" of the fuel we use (i.e., the additive package used by the brand). That is another down-the-rabbit-hole conversation.

[Hosstage]

What does your owners manual recommend?

[Bluenoser]

Somewhat little know fact is that higher octane fuel burns at a lower temperature than fuel of a lower octane at a given power setting. Many people believe it to be the opposite. Not suggesting it will harm the engine but lower octane does produce more heat.

[Hosstage]

My understanding is that higher octane fuel burns slower, which allows for more compression. It will actually lower horsepower in a motor set up with lower compression for lower octane fuel.

[Twisties]

2 hours ago, TSConver said:

 

The 1250s have knock sensors, the 1200 WC motors do not.

Well, this post is in the shiftcam forum.

[Cap]

4 hours ago, Bill Murray said:

..That is another down-the-rabbit-hole conversation.

 

And then, there is the altitude where you operate...  Sometimes at high altitude, 89 is the best you can find. 

[Hati]

2 hours ago, Hosstage said:

My understanding is that higher octane fuel burns slower, which allows for more compression.

 

The higher the octane rating the more the fuel can be compressed before it self ignites. This self-ignition is what is called "knock". Since timing of the ignition is everything for an engine, doesn't take too much imagination to work out what badly timed ignition due to lower octane fuel can damage in your engine. 

 

 

6 hours ago, Daveyator said:

I think it’s well know that premium gas and gas grades in general have always been a way to get us to pay more for gas but is only absolutely required in very few engines.

 

I think you couldn't be more wrong if you tired. As per above, the higher your engine's compression ration, the higher the octane requirements so the fuel detonates on ignition from the spark plug, not self ignite like what happens in a diesel engine. There is a minimum recommendation for a reason, nothing to do with trying to rip people off. High performance engines generally need higher octane fuel because the compression ratio of those engines is higher. Higher compression = more power output.

 

The factory recommendation is there for a reason. BMW engineers do not get a retainer form oil companies to herd their customers to the more expensive fuel bowsers...

[Steveyacht]

I suppose I'll stick with the Premium grade, no sense in being that frugal!

[Rougarou]

My 200

7 hours ago, Hosstage said:

What does your owners manual recommend?

 

My 2006 RT says

Recommended fuel grade
Super Plus (premium), unleaded
98 ROZ
Fuel grade, usable with
power- and consumption related
restrictions
Regular, unleaded
91 ROZ

 

My 2019 GSA says

Recommended fuel quality

Super unleaded (max. 15 %
ethanol, E15)
89 AKI (95 ROZ/RON)
90 AKI
Alternative fuel quality
Normal unleaded (with performance
penalty) (max. 15 %
ethanol, E15)
87 AKI (91 ROZ/RON)
87 AKI

 

All that gibberish means to me is that I've been fine running regular fuel mostly

 

'memba, there's "recommended" and "required", if it is not "required", tis only a "recommendation" that you use a specific, kinda like "I recommend you to eat at McDonalds", I don't "require" you to eat there.

[Daveyator]

18 hours ago, Rougarou said:

My 200

 

My 2006 RT says

Recommended fuel grade
Super Plus (premium), unleaded
98 ROZ
Fuel grade, usable with
power- and consumption related
restrictions
Regular, unleaded
91 ROZ

 

My 2019 GSA says

Recommended fuel quality

Super unleaded (max. 15 %
ethanol, E15)
89 AKI (95 ROZ/RON)
90 AKI
Alternative fuel quality
Normal unleaded (with performance
penalty) (max. 15 %
ethanol, E15)
87 AKI (91 ROZ/RON)
87 AKI

 

All that gibberish means to me is that I've been fine running regular fuel mostly

 

'memba, there's "recommended" and "required", if it is not "required", tis only a "recommendation" that you use a specific, kinda like "I recommend you to eat at McDonalds", I don't "require" you to eat there.

That’s kinda what I was getting at. 

[Daveyator]

22 hours ago, Hati said:

I think you couldn't be more wrong if you tired. As per above, the higher your engine's compression ration, the higher the octane requirements so the fuel detonates on ignition from the spark plug, not self ignite like what happens in a diesel engine. There is a minimum recommendation for a reason, nothing to do with trying to rip people off. High performance engines generally need higher octane fuel because the compression ratio of those engines is higher. Higher compression = more power output.

 

The factory recommendation is there for a reason. BMW engineers do not get a retainer form oil companies to herd their customers to the more expensive fuel bowsers...

So, if the only thing standing between you and a tow truck is a gas pump with 87 octane in it you won’t gas up because it might hurt your engine? In a lot of states here in the US it’s hard to find anything higher than 91. On top of that as I’m sure you know, the octane rating of fuel starts dropping almost immediately after coming out of the pump. If these engines were so ultra sensitive to lower octane fuels, we be given stern warnings and possible directions to use octane boosters. But they’re not. Will they run their best on lower octane fuel? No. But will they be damaged or prematurely worn by using it? No. Manufacturers know there’s huge variances in fuel grades available. They account for that in engines made for general consumers.

Edited September 16 by Daveyator
Spelling

[Bluenoser]

Here in Canada most 91 octane fuel is ethanol free.  87 octane contains 10% or more ethanol.  I do my best to avoid ethanol.  It may not make much difference if burned right away but when left sitting in the bike for long, it absorbs moisture and causes corrosion.

[Hati]

2 hours ago, Daveyator said:

So, if the only thing standing between you and a tow truck is a gas pump with 87 octane in it you won’t gas up because it might hurt your engine?

 

No, I never said that. I simply dismissed your conspiracy theory on the usage of higher octane fuel.

 

I have used in the past and will use in the future lower octane if there is nothing else available, but under normal circumstances I go for the recommended grade or better. 

 

2 hours ago, Daveyator said:

I’m sure you know, the octane rating of fuel starts dropping almost immediately after coming out of the pump

 

No, I don't, mostly because it's not true. Most fuels will hold their octane rating for a few months. Don't just believe me, do your own research instead of repeating hearsay 

 

2 hours ago, Daveyator said:

If these engines were so ultra sensitive to lower octane fuels, we be given stern warnings and possible directions to use octane boosters.

 

Nobody, not even the manufacturers said that these engines are "ultra sensitive". There is a difference though to regular use opposed to occasional use of lower grade fuel.

 

2 hours ago, Daveyator said:

But will they be damaged or prematurely worn by using it? No.

 

Not true, if used all of the time. But hey, feel free to believe whatever you like and fill your bike with whatever grade of fuel you want. No skin off my nose :P

[9Mary7]

Wow.....this discussion took a turn

[ADulay]

We have 91 and 93 octane here locally (10% ethanol) and 90 octane non-ethanol.

 

I generally use the 90 octane "non" when the pump is available as it's a single source pump and I won't be getting two gallons of whatever went there before me while using the other pumps.

 

I have had to use the 87 octane when traveling way out west as at a lot of fueling stations, that's all they have.   When forced to use the 87 octane I simply ride a bit more conservative (no racing that 18 year old clown in daddy's Porsche) until the next decent fill up.

 

I do like the non-ethanol fuel as it appears to give me slightly better mileage but that might also be due to the higher elevations when out west.

 

I generally run through almost 2 tanks a week here at home so the ethanol problems really don't come into play with me but I still like the non-ethanol 90 octane even in spite of the higher price locally.

 

AD

[ADulay]

5 hours ago, ADulay said:

I generally run through almost 2 tanks a week here at home so the ethanol problems really don't come into play with me but I still like the non-ethanol 90 octane even in spite of the higher price locally.

 

AD

Well, no sooner did I post that when it turned out I needed fuel coming back from the range this afternoon.

 

Checked the prices and sunofagun it turns out that 90 octane non-ethanol is the same price as 91 octane with ethanol at my local Mobil station.

 

AD

[Skywagon]

Dang Andy.. it’s about a buck more per gallon on ethanol free in Houston. I still buy it. 

[Dave_in_TX]

22 hours ago, Hati said:

 

No, I never said that. I simply dismissed your conspiracy theory on the usage of higher octane fuel.

 

I have used in the past and will use in the future lower octane if there is nothing else available, but under normal circumstances I go for the recommended grade or better. 

 

 

No, I don't, mostly because it's not true. Most fuels will hold their octane rating for a few months. Don't just believe me, do your own research instead of repeating hearsay 

 

 

Nobody, not even the manufacturers said that these engines are "ultra sensitive". There is a difference though to regular use opposed to occasional use of lower grade fuel.

 

 

Not true, if used all of the time.

22 hours ago, Hati said:

 

No, I never said that. I simply dismissed your conspiracy theory on the usage of higher octane fuel.

 

I have used in the past and will use in the future lower octane if there is nothing else available, but under normal circumstances I go for the recommended grade or better. 

 

 

No, I don't, mostly because it's not true. Most fuels will hold their octane rating for a few months. Don't just believe me, do your own research instead of repeating hearsay 

 

 

Nobody, not even the manufacturers said that these engines are "ultra sensitive". There is a difference though to regular use opposed to occasional use of lower grade fuel.

 

 

Not true, if used all of the time. But hey, feel free to believe whatever you like and fill your bike with whatever grade of fuel you want. No skin off my nose :P

But hey, feel free to believe whatever you like and fill your bike with whatever grade of fuel you want. No skin off my nose :P

My 2020 GS did fine on a steady diet of 87 octane for 93k miles of ownership.

[Rinkydink]

I have had to run a ton of 87 in my travels. On my 4th RT starting in ‘04. Sure I prefer 89 but sometimes 87 is all there is. I’ve had no pinging problems to date. 

[Skywagon]

SteveYacht... I couldn't tell from your original question which RT you have.  My 2014 manual calls for 89.  I usually buy premium but would have no issue using 89 and I have on many occasions.  I buy ethanol free when I can find it.  Fuel is cheap, engines not so much.

 

BMW has a bit of a reputation for not always recognizing warranty when the owner uses fluids be it fuel, oil, gear, brake fluid...etc it you don't follow the recommendations and document the fluids if you are a DIY'er.  I truly believe there is no way BMW would list 89 as their recommendation if it wasn't adequate for the engine.  They don't want warranty claims based on their recommendations to use certain fluids.

 

I think that was the intent of your original post.  I'm on my 3rd RT.  I've not had any issues caused by fuel or other fluids.  I don't always buy BMW brand, but I stay within their specs.  

 

Which RT are you riding?  Sorry if I missed it.

[Hati]

6 hours ago, Dave_in_TX said:

My 2020 GS did fine on a steady diet of 87 octane for 93k miles of ownership.

 

I don't remember exactly when did BMW introduce the knock sensors, but your shift cam definitely has it. It then retards the ignition to allow for the lower grade fuel and that manifests in lesser performance. Feel free to deprive yourself of performance for the sake of a few dollars. 

 

Personally I don't care what you or anyone else fills their bikes with. You bike, your money. But I do have a problem with misinformation. Misinformation such as motor vehicle manufacturers having a deal in place with fuel companies to con the public into using higher grade than necessary fuel.

[lkraus]

 

If lower octane was unacceptable, the manual would not mention it.

 

My Hexhead manual recommends (98RON/93AKI), but it runs just fine on the listed alternate (95 RON/91 AKI).  It has a sensor to detect and stop knock with a timing adjustment, which does reduce power and slightly reduces fuel mileage. A few times when 87 AKI was the only option, a  couple gallons added to the gallon in reserve got me to another station with 91 or 93 without pinging.  I only detected the power loss as reduced acceleration when passing on back roads.  

 

The Wethead R1200 engine did not have a knock sensor, and recommended only 91 AKI. The 87 AKI option required a programming change by a dealer. 

 

 The knock sensor is back on the R1250 engines, and the alternate, lower octane, fuel option is back in the owners manual.

 

Higher than recommended octane will not provide any benefit, while lower than recommended octane may damage your engine. Within the acceptable range, lower octane will slightly reduce power and fuel mileage.  You may not notice the performance difference in everyday riding, and the lower price/gallon may outweigh the reduced mileage.

 

It's not that hard to just follow your manual.

[Hati]

6 hours ago, lkraus said:

Higher than recommended octane will not provide any benefit

 

Generally, you are correct. Some parts of the world though, like mine for example, the higher grade fuel is also cleaner, measurably. Leaving you with less sediments in the tank and cleaner filters for longer. Does give you a tiny bit of extra power, but not enough to balance the higher price you pay. Don't know how the American fuel industry works, so speak of only the Australian conditions in this regard.

[Dave_in_TX]

On 9/17/2023 at 10:16 PM, Hati said:

 

I don't remember exactly when did BMW introduce the knock sensors, but your shift cam definitely has it. It then retards the ignition to allow for the lower grade fuel and that manifests in lesser performance. Feel free to deprive yourself of performance for the sake of a few dollars. 

 

Personally I don't care what you or anyone else fills their bikes with. You bike, your money. But I do have a problem with misinformation. Misinformation such as motor vehicle manufacturers having a deal in place with fuel companies to con the public into using higher grade than necessary fuel.

Yes, the 1200 wetheads did not have a knock sensor but the 1250, 1200 hexhead and 1200 camhead did. As for lower performance, I did not notice any difference, the few times I ran higher octane in my 1250. I also ran 87 for tens of thousands of miles without problems on my 1200 wethead which had 132k miles on it when sold. If spending more on gas makes you happy, feel free to do so.

 

Personally, I am more concerned with using top tier gas when available, rather than getting higher octane.