In my case, higher octane petrol has made a huge improvement!
Before the last two fill-ups, I'd used exclusively 95 RON, from Esso, BP, Total, Tesco & Morrisons. The engine was inclined to what sounded to me<mytubeelement =""bundle":"label_delimitor":":","percentage":"%","smart_buffer":"Smart Buffer","start_playing_when_buffered":"Start playing when buffered","":"","desktop_notification":"Desktop Notification","continuation_on_next_line":"-","loop":"Loop","only_notify":"Only Notify","estimated_time":"Estimated Time","global_preferences":"Global Preferences","no_notification_suped_on_your_browser":"No notification style suped on your browser version","video_buffered":"Video Buffered","buffered":"Buffered","hyphen":"-","buffered_message":"The video has been buffered as requested and is ready to play.","not_suped":"Not Suped","on":"On","off":"Off","click_to_enable_for__site":"Click to enable for site","desktop_notification_denied":"You have denied permission for desktop notification for site","notification_status_delimitor":";","error":"Error","adblock_interferance_message":"Adblock or similar extension is known to interfere with SmartVideo. Please add to adblock whitelist.","calculating":"Calculating","waiting":"Waiting","will_start_buffering_when_initialized":"Will start buffering when initialized","will_start_playing_when_initialized":"Will start playing when initialized","completed":"Completed","buffering_stalled":"Buffering is stalled. Will stop.","stopped":"Stopped","hr":"Hr","min":"Min","sec":"Sec","any_moment":"Any Moment","popup_donate_to":"Donate to","extension_id":null,"prefs":"desktopNotification":true,"Notification":true,"logLevel":0,"enable":true,"loop":false,"hidePopup":true,"autoPlay":false,"autoBuffer":true,"autoPlayOnBuffer":true,"autoPlayOnBufferPercentage":42,"autoPlayOnSmartBuffer":true,"quality":"large","fshd":false,"onlyNotification":true,"enableFullScreen":true,"saveBandwidth":true,"hideAnnotations":false,"turnOffPagedBuffering":true" ="preferencesUpdated" id="myTubeRelayElementToPage"></mytubeelement><mytubeelement =""loadBundle":true" ="relayPrefs" id="myTubeRelayElementToTab"></mytubeelement> like pinking a lot of the time. And though it always sounded fine at motorway speeds, on returning on slower roads it would sound rougher in general than before the fast stretch.
The last two fill-ups have been 99 RON Tesco Momentum99, then 97 RON BP Ultimate. It's like a different car! Now at low revs the engine makes that healthy rorty sound everyone else talks about with no hint of pinking; and it makes no difference whether the engine is cold or has just done a fast run.
I don't know about an overall difference in power, but I'm more willing to put my foot down now that it sounds so much healthier when I do.
My fuel consumption has actually worsened a little with the higher octane ""“ possibly because of this now feeling freer with my right foot.
When the car was new, I noticed after a couple of journeys that it had been supplied with the oil overfilled (by maybe 7 mm, from memory). As soon as I discovered this, I syphoned out the excess (less than a pint), but maybe the damage had already been done. The manual says that overfilling is a Very Bad Thing ("Do not start the engine"). In particular, I understand that it can lead to oil coating the oxygen sensors in the exhaust system ""“ maybe they are now misleading the ECU, causing pinking unless counteracted by fuel with sufficiently high octane (which by
definition inhibits pre-ignition=pinking)?
Or maybe it's just the different lubricant and other additives in the premium fuel? Or sheer coincidence""¦