Consequences of using lower octane

On the '07 R1200GS, 92 octane is recommended, but 87 octane can also be used. What happens to power, fuel mileage, and engine life/reliability if the 87 octane is used?

I don't think engine life and reliability are affected, but I get about 20 less miles on a tank. It feels less powerful, but I have no way to prove it.

The biggest issue with using lower octane fuel is "pinging" or pre-detenation. And surprisingly, it can be controlled somewhat by your riding style, and where you ride (temperature), and how well the engine is tuned.

It's been recommend, by some, to try a tank of low octane. Ride normally, and listen for "pinging" on acceleration. If you get "pinging", move up to mid octane and try again. If it still "pings", move up to high octane fuel. If it still "pings", get the engine serviced. After service, start the process over again.

Oh, if in your trials, you do get "pinging", don't accelerate has fast/hard to minimize "pinging" while you use up the tank. If it's to bad, then drain the tank and use the fuel in something else (lawnmower).

As for fuel economy, eh... some report better fuel mileage with lower octane, some don't. Most likely if you do get better fuel mileage, it's due to not flogging it all the time.

For engine wear, if you get "pinging" that can cause issues.

Personally, I have an '00 R1150GS, and I run low octane most of the time. I keep the engine perfectly tuned, and I don't flog it, so I can get by with low octane fuel. But in the summer, I sometimes move up to mid octane fuel because excessive heat will induce "pinging". I get about 40-45 mpg on average, btw.

P.S.
This is 'general' information, that can be applied to cars as well.

Octane is a hydrocarbon liquid that is used as a reference standard to describe the tendency of gasoline, petrol, or benzin fuels to self ignite during compression prior to the desired position of the piston in the cylinder as appropriate for valve and ignition timing. The problem of premature ignition is referred to as pre-ignition and also as engine knock, which is a sound that is made when the fuel ignites too early in the compression stroke.
Severe knock causes severe engine damage, such as broken connecting rods, melted pistons, melted or broken valves and other components. The octane rating is a measure of how likely a gasoline or liquid petroleum fuel is to self ignite. The higher the number, the less likely an engine is to pre-ignite and suffer damage.

Isooctane (upper) has an octane rating of 100 whereas n-heptane has an octane rating of 0.


The most typically used engine management systems found in automobiles today monitor the level of knock that is being produced by the fuel being used. In modern computer controlled engines, the timing of the ignition will be automatically altered by the fuel management system to reduce the pre-ignition to an acceptable level.
The octane rating of gasoline is measured in a test engine and is defined by comparison with the mixture of 2,2,4-trimethylpentane (iso-octane) and heptane that would have the same anti-knocking capacity as the fuel under test: the percentage, by volume, of 2,2,4-trimethylpentane in that mixture is the octane number of the fuel. For example, petrol with the same knocking characteristics as a mixture of 90% iso-octane and 10% heptane would have an octane rating of 90.<SUP id=cite_ref-0 class=reference>[1]</SUP> A rating of 90 does not mean that the petrol contains just iso-octane and heptane in these proportions, but that it has the same detonation resistance properties. Because some fuels are more knock-resistant than iso-octane, the definition has been extended to allow for octane numbers higher than 100.
Octane rating does not relate to the energy content of the fuel (see heating value). It is only a measure of the fuel's tendency to burn in a controlled manner, rather than exploding in an uncontrolled manner. Where the octane number is raised by blending in ethanol, energy content per volume is reduced.

A US gas station pump offering five different (R+M)/2 octane ratings


It is possible for a fuel to have a Research Octane Number (RON) greater than 100, because iso-octane is not the most knock-resistant substance available. Racing fuels, avgas, liquefied petroleum gas (LPG), and alcohol fuels such as methanol may have octane ratings of 110 or significantly higher. Typical "octane booster" gasoline additives include MTBE, ETBE, isooctane and toluene. Lead in the form of tetra-ethyl lead was once a common additive, but since the 1970s, its use in most of the industrialised world has been restricted, and its use is currently limited mostly to aviation gasoline.
[edit] Measurement methods

[edit] Research Octane Number (RON)

The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane.
[edit] Motor Octane Number (MON)

There is another type of octane rating, called Motor Octane Number (MON), or the aviation lean octane rating, which is a better measure of how the fuel behaves when under load, as it is determined at 900 rpm engine speed, instead of the 600 rpm for RON.<SUP id=cite_ref-1 class=reference>[2]</SUP><SUP id=cite_ref-2 class=reference>[3]</SUP> MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON, however there is no direct link between RON and MON. Normally, fuel specifications require both a minimum RON and a minimum MON.<SUP style="WHITE-SPACE: nowrap" class=Template-Fact>[citation needed]</SUP>

With European motorcycles do not get RON and MON mixed up.

87 RON (in the USA) is equivalant to approx 95 MON (in the U.K.) Check with the bike manufacturers sticker if the rating is in MON or RON.

I've found all our 1150 Oilheads to run fine with 87 RON

my '07 GS has pinged on hot summer days when flogged on steep hills since new. Dealer claims that it's in perfect tune. I've always used 93 or the highest available

It's really a simple formula and we all know it. Better fuel runs better (and costs more). My '94 GSPD seems happy with 87 octane. It typically runs better in cooler weather, but even better fuel doesn't help in the summer around here. Air cooled engines like cooled air, not 110 degree months.

Thank you for the info on gasoline octane ratings.

Pinging is your risk with lower octane. As for power output, it should be somewhat similar (I do not think even the newest 1200 have variable cam timing to correct detonation, which would protect you from pinging by decreasing power output).

Now that E10 is everywhere, higher octane are usually more loaded with alcoohol than lower octanes. Hence using high octane means more ethanol, with the issues related to melting plastic tanks, swelling o-rings, low fuel efficiency, fuel separation, etc etc. I'd stick with the lowest octane that does not detonate, for that reason. However, in TN summer, only 93 does not detonate :eek1

When I had my 06 R12GS, I always ran on 87 octane with no issues whatsoever. The only time the bike ever pinged was if I was stupid and tried to take off in something other than first gear :huh
When I sold the GS and bought an 05 RT, I HAD to use at least 89 octane because of the different first gear ratio

I've nearly never used anything but regular on my R1200 bikes, both the GS and the ST, and in over 100K miles I have never heard it ping except when dogging it under 1700 RPM. 1700 RPM is when the knock sensors kick in, so you should never risk damage to your motor.

On the R1100/1150 series, this is not necessarily the case.

Jim

If you are pinging over 1700 RPM your bike is NOT working correctly. Usually the knock sensor(s) is/are not working right.

Jim

it stops if I hold on or increase the throttle. borrowing a term from a cage owner's manual, it's just the initial "tip-in" that causes it

92 RON or 92 AKI...???

See,... 92 RON is 87 AKI.......and 95 RON is 90-91 AKI

but also 98 RON is 93-94 AKI

AKI is popular in Europe...RON popular here stateside.

MY '05 GS had this sticker on the gas cap...


....and my current GSAdv has this on the gas cap...


....SOooooo......89 AKI is close to a 95 RON...me thinks..don'tcha think????

On *US* Market bikes, the sticker AKI number is what you match up to the octane number on the pump.

In the US, AKI is the average of RON and MON. In Europe, they typically bill only the RON number on the pump. By averaging the two together, the US system tends to take into account the spread between RON and MON. The difference between them is called sensitivity. There are some fuels like ethanol which have a large spread between RON and MON.

So, if you have a USA market BMW motorcycle you use the AKI number, which in this case is 89, which corresponds to midgrade at most stations.

You do not translate it to a European number. BMW already did that for you and put the right number on the sticker.

Octane number is a rating that indicates the resistance of the fuel to *detonation*. This is widely misdescribed on the internet as pre-ignition, but it is not the same thing.

In a normal engine cycle, the fuel is ignited by the spark and combustion while rapid by human standards, is not really an explosion. Normal combustion is an orderly process which consumes the fuel mixture completely and produces a smooth, steady rise in cylinder pressure.

In detonation from low octane, the ignition starts with the spark, as normal. But as the burn proceeds, it breaks down into an explosion, which produces a rapid and sudden rise in cylinder pressure. This produces the "pinging" sound and is literally like a jackhammer going off in the engine. Mild detonation usually isn't harmful, it just makes the pinging sound and results in a reduction of power output and increase in pollutants.

Most modern car engines and some motorcycles like the late model R1200 engines, have knock sensors that detect pinging. Most engine computers will retard ignition spark timing to lower combustion pressure and stop the pinging. Some will also richen the mixture or change cam timing if available or reduce throttle input. Just depends on the engine and the software measures employed.

Severe or prolonged detonation will damage the engine.

I agree with Guzzler. If I use low-octane in the HP2 and *don't* flog the engine, it tends to be slightly more powerful (relative to the not flogging it) than using high-octane fuel. I also notice I tend to get a little better milage with low-octane fuel. But if I plan on really wrenching on the throttle, I put high-octane fuel in, just to be safe.

I once badly fouled my sparkplugs using low-octane fuel and really cranking the bike. It only took one tank of gas, too.

Regarding the R1100/1150. Why would that be?

Especially with the R1100, it is a low compression air/oil cooled motor with a primitive fuel injection system that would seem to lend itself to being gasoline tolerant. I know on my R1100GS I can't tell any difference whatsoever with differing grades of fuel. I would think this would be the case with all of the oilheads, hexhead different story of course.

No knock sensors on the 1100/1150 bikes. When the motor is hot and you dog it, it will often ping, sometimes excessively. The hotter the motor the more the ping. A good tune and high octane gas usually prevents it.

Jim

My R1200S engine asks for 99 octane which is $UPER expensive and only available at the track. Big arse throttle bodies, more compression, etc make it work fine.

Anti knock lets me run 89-93 octane on the street. The owner's manual approves is as well, gas mileage drops too. Very hard to notice because the anti knock works so damn well.

Funny thing is trying to get it start on a really cold morning, like today at 22 degrees, with 99 in the tank. The Mid-grade stuff ignites much easier in the cold, easier start ups.