Fuel Octane Rate

[Croc]

Can anyone tell me (stupid question!!) if the octane rating of the fuel makes any percievable difference to the performance? I generally use 95 octane but have also used 97 and now I see that at a pump down the road they are selling 99 octane? Any views?

Croc

[MikeCam]

We colonists use a weirder way of measuring so can offer little help. But my memory suggests that unless you get pinging under load in high heat, then the lowest octane you choose is safe for the FI system with no perceptible performance differences.

[Deans BMW]

You get the highest power and highest milage with the lowest Octane that you can run without pinging. You can use lower Octane in cooler weather and at higher elevations, conversly lower elevation and hotter weather higher octane would be required to prevent pinging, each bike will very in its needs depending on the conditions of the combustion chambers. The R1200 Hexheads and the new K bikes will not ping due to a knock sensor that will retard timing if a knock in "heard".

[The Kurch Man]

I run 89 (mid grade) and have no problems. The BMW dealer suggested it and it runs fine. Got a speeding ticket yesterday to support the fact it runs like a scared rabbit.

[boxermania]

Just to assist with the understanding of oil based fuels.

The octane rating of Grade 87, 89, 91, or 93 (typical fuel grades) have nothing to do with power. As Dean had mentioned a gallon of gasoline has the same caloric value (BTU's) irregardless of the grade.

What the grade refers to is the additive package ........the additive package serves many purposes one of them being the ability to somewhat quench the explosive nature of gasoline and make it behave more like a controlled burn. This is what one experiences during detonation, or the ability to ignite gasoline by means other than by the spark plug firing.......

The source of detonation is normaly atributed to one of two conditions, A) Lugging the engine, running at low rpm, under heavy load on higher gears. or B) Due to carbon deposits in the combustion chamber which will glow red and ignite the incoming gas mixture.

So in closing, depending on your driving style use the least expensive gas that will allow you to run without detonation.....no damage will result to the engine, nor willl you lose performance and you will save some cash in the process.

Ahhhhh.....it's good to be back......been busy like a rabbitt

[wncbmw]

What Dean says makes sense to me and matches my experience. I used to use high octane (93) but switched to mid grade after people on this site recommended the lowest octane without pinging. No problems for a while, until Friday, I got some pinging under hard acceleration, with temps in the mid-80s. Guess I need to switch back for the summer.

[Croc]

Thanks for all the replys. Somehow I knew there would be a few!!

I shall switch back to the lowest we have here in the UK which is RON 95 and save a few bob! (with fuel at 90 pence a litre!)

cheers
Croc