What octane for 2.5L normally aspirated Z3

[MattInSV]

I’m in California and have the choice (typically) of 87, 89 and 91 octane at US $4.60, 4.80 and 4.90/ gallon respectively. Each is ”up to 10% Ethanol”

Is there a benefit to the higher octane fuels for my 2000 z3 2.5L engine? I don’t have the owner’s manual.

thanks,

Matt

 

[andyglym]

I’m in California and have the choice (typically) of 87, 89 and 91 octane at US $4.60, 4.80 and 4.90/ gallon respectively. Each is ”up to 10% Ethanol”

Is there a benefit to the higher octane fuels for my 2000 z3 2.5L engine? I don’t have the owner’s manual.

thanks,

Matt

There's a good clip on YouTube from a motoring show called 5th Gear with regards to Octane and its performance advantages, It's an old clip but clear benefits, if marginal, to the 2.2 VW Golf GTi.

 

[andyglym]

 

[MattInSV]

Thanks! I do recollect watching it before ( 3 cars and 3 fuels on the dyno) and really seeing some performance gain with the top end fuel only with the sportier car.

Our other cars, like the Fiat Abarth (2015) and Land Rover (2007) will run on mid grade fuel but the manufacturers recommend high octane (what we call Super Unleaded here) because of the high engine compression. I wasn’t sure if there was any such recommendation for the z3 to reduce pinging and prolong engine life?



Regards,

Matt

 

[Mike Fishwick]

All BMW engines are optimised for use on 98 octane, but later engines such as the Z3 will tolerate anything down to about 91 octane - remember that in Europe we use the RON octane ratings. Use of lower octane ratings will cause the ignition timing to be retarded until detonation is avoided, with a consequent loss of engine output and increased fuel consumption. Try reading the Owner's Manual.

Even with European fuel, which is of far better quality than the filth sold in America, I find that the difference between 95 and 98 octane is about a 10% improvement in fuel consumption, for a 3% increase in cost - you get what you pay for!