Fuels are formulated differently all over the world. Even in the US deferent regions (and metropolitan areas) have deferent formulas. As a general rule for US SLK's 91 is the preferred octane rating. Also despite popular (wrong) belief using a higher rated octane will not enhance performance, but will actually degrade performance and add pollutants from unburned fuel.
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Thank you, thank you. [
] Finally, I know there is at least one other person who understands this. The octane number is simply a quantitative measure of the fuel's ability to prevent 'knock' or pre-ignition, which is typically an issue at higher atmospheric pressures such as at the coast. It is done by adding additives that actually reduces the speed at which the fuel ignites. (Very important for some high-performance engines at high ambient pressure, to prevent damage.)
That is the reason why Aus fuels are typically a higher octane - most cars run close to the coast (becuase 80% of Aussies live on the coast, or close to it.)
cheers
roadsta
All true, but remember that the SLK350 recommends 91 octane as a minimum, not as standard. The car has 10.7 to 1 compression. That's a lot. If you run 87 octane your car will be riding the knock sensor and the car will be so retarded it will run poorly. On the other hand, running 93 to 95 will not hurt one bit, or hender mileage as the pulse width on the injectors will decrease after the unburnt fuel is seen exiting the exhaust. But as stated earlier, higher octane does not mean higher performance. It's all about the temp of that combustion chamber, which increases with higher compression. 91 minimum is also based on the heat range of the spark plugs that are in the car. If you were to increase or decrease that heat range, your octane requirement will change also to prevent detonation or poor operation.roadsta - 2/14/2005 5:40 AM
Thank you, thank you. [
The octane number is simply a quantitative measure of the fuel's ability to prevent 'knock' or pre-ignition, which is typically an issue at higher atmospheric pressures such as at the coast. It is done by adding additives that actually reduces the speed at which the fuel ignites. (Very important for some high-performance engines at high ambient pressure, to prevent damage.)
That is the reason why Aus fuels are typically a higher octane - most cars run close to the coast (becuase 80% of Aussies live on the coast, or close to it.)
cheers
roadsta
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