if your outside EC (like me) you can order your BMW without cats, talk to your dealer to include option code 199 !

 

If your car asks for 91 or better octane rating most of the time using it is a very good thing.

Octane ratings in the US may show on the pump but in buying "91" octane there is an acceptable range of real Octane reading from the gas supply...sometimes it might be 91 other times it might dip below even though youre paying a premium for the gas.

When high performance engines arent reading the Octane rating they need to produce the proper combustion, the computer ignition will try and adjust the firing rate looking for an optimum timing based on the combustability. this can cause the 'pinging' that people can sometimes hear from their car when one steps on the gas and gets lag. Its much more obvious in cars with Turbos or Superchargers...ultimately, this leads to poor fuel economy and potential early parts wear etc. Higher octane in a high performance car means better response and overall better performance/economy.

Octane is good for BMWs...

 

In Hong Kong we have 98RON only, but somehow the oil companies still managed to sell 2 types of 98 - one normal & one expensive (e.g. V-Power, F1 Synergy etc.). I just buy the normal 98.
In Japan, premium is 100RON, & regular is I think 97RON.
The US fuel got bad press as several engine related problems due to bad fuel happened mostly in US only, e.g. the BMW V8 during early 90's. This is due to the high sulphur levels in US fuel.

 

My bad

ABC