I was just looking in my Haynes manual (I had a reason, not just casually reading it !) - it's the old type that provides more info.
I noticed a section on the Motronic 2.5 & in here it says that
"The Motronic M 2.5 system fitted to 16-valve models compensates for small changes in fuel octane rating automatically as part of the knock control function"
Fair enough, nothing new there, but it goes on to say -
"The control unit contains 2 ignition timing maps, one for high octane fuel & one for lower octane. If the engine knocks frequently, the control unit switches to the low octane map. A steady period free of knocking will cause a switch back to the high octane map. On the C20XE engine the maps are for 91 & 95 octane; on the others they are for 95 & 98 octane."
I was under the impression that the C20XE could fully utilise 98, but after reading the above it appears that 95 is the maximum. Going on that premise (& assuming that 95 RON is actually 95) is there a benefit from using the high octane fuel in a C20XE.
I have never tried 98 RON & so cannot comment. Can somebody help my confusion here?