Octane vs gas mileage

[disco_jon75]

I've been putting premium in my bike since I bought it two or three months ago. Do I get better gas mileage, better engine life and performance, or should I just go with regular?

[towerworker]

I have an 04 dual spark. I can consistently get better fuel milage using mid-grade (91 octane) rather than hi-test (93) 50 to 52 mpg at highway speeds and not dogging it.

However I get some pre-detonation under low engine speed/high throttle operation. If I keep the rpm's up and use the gears I don't get the pinging.

I'm not an authority so I can't tell you the long term effects of pre-detonation although all I have read and hear tells me it is to be reasonably avoided. I have never run straight regular fuel (87 octane)

Wayne

[Arbee]

I am starting to get the feeling that we use a different scale??? as our standard fuel
is 91 octane with Premium 95 octane and Super Premium 98 octane... go figure

[Beemeridian]

11

[dnat928]

In my 2002R, I initially used the 92 octane, but after a while, tried the 87. I did not notice any difference in performance or mileage. I did not notice any knocking, but that was in the winter months. Lately, I have been using the 92, during warmer weather time. Again, no noticeable differences. Definitely, if you try the lower octane gas and you detect knocking, switch upward in octane ASAP. If you get no knocking, you may well be OK with the lower octane gas.

[Ves]

Far as I understand it, octane prevents knocking because it makes the gas mixture harder to ignite. If the gas is harder to ignite, it pretty much means it will not burn as efficiently as a low octane gas. So, unless you need high octane to prevent knock, you're better off using low octane, and will probably get slightly better mileage with it.

That's generally true of any "additive" you put in gas (unless it's oxygen rich)... it will make the gas more difficult to burn.

[Arbreacames]

I fully agree with everything written above. Notice, however, that on engines equipped with knock sensors (e.g. R1200R, cars, etc.) the message will be a little different. In those vehicles, the sensor will avoid knocking by retarding the timing, and lower octane may give worse mileage/power even with no knocking.

[boxermania]

This is a complicated subject with multiple answers....let me explain:

Mass production - The object is to produce a product that will fit a defined range, that means that some will be better than others.

State of tune - Some bikes are in a better state of tune than others and that affects its operation.

Gasoline caloric value - Burning on gallon of gasoline generates ~ 119K BTU's. Contrary to popular belief Regular, Intermediate and Super have the same caloric value and hence there is no mileage advantage. What defines the pump ranges is the additive package, which among all the components there is one that retards the naturally explosive tendencies of the gasoline upon being ignited.

Engine operational range - IC engines are not designed to be lugged, in other words, demand a high output at low engine rpm. When this happens the result is called pinging or knocking and is for the most part quite noticeable. Normal human response is to ease of the gas or drop down a gear or two. Gone and forgotten.

Detonation - This is sometimes confused with pinging or knocking, however, it is quite different in its origin. Internal combustion engines of the 4 cycle variety depend on the firing of a compressed gas mixture at the right time for the best efficiency (power). Basically once the design has been arrived at there is little that can change except the time when the spark occurs (no, I will not be addressing the ability to change the valve timing on the more sophisticated systems today as it doesn't apply to this discussion) In it's most simple form, detonation occurs when unburned pockets of A/F mixture are ignited ahead of the timed spark by increased temperatures and pressures in the combustion chamber. In other words, you engine wants to become a diesel. These explosions are quite severe and will in short time damage your engine components.

So with the above as a starting point:

Keep your bike at a reasonable state of tune; it will pay on the long run.
Don't lug your engine, drop down a gear or two.
From time to time operatre the engine in the upper rpm ranges (do it safely, in lower gears if needed)
Run the gas that your mass produced motor is happiest with. I had several engine mods on my bike and was very proud of it and never ran anything other than 89 gas.

Lastly, as Carlos (abreacames) so stated this is not applicable to the R1200 or any other bike with knock sensors as the spark will be retarded, the engine will operate less efficiently and the gas mileage will be less. Can't have your cake and eat it too.