It's absolutely correct that using fuel of higher grade than your engine is tuned for won't provide any benefit - so yes on the face of it if your car is specified to use 91 than that's all you should need.
The PROBLEM is that IMO a lot of our 91 grade fuel isn't actually deserving of the label - ie. it clearly performs below it's specification.
We use 95 instead of 91 in our 2015 TH (BUT NOT 98) - because we also see a clear improvement in smooth running, consistency of performance - ie. runs great on a hot OR cool day - and improved mileage.
Why do I think most 91 grade doesn't perform to spec? (I actually don't think ANY does but I'm trying to be fair) - read the paragraph above - ie. if 91 was performing to spec then we SHOULDN'T see such improved performance from using a higher grade.
My wife and I argued about this for YEARS since getting the car new in April 2015 - ie. she insisted on using 91 because it was specified and was cheaper. She couldn't deny the improved performance whenever I put 95 in it but for years she held out until I pretty much insisted we switch permanently to 95. Not only did we see the usual pretty much immediate improvement (we're habitual "fill it when it's down below 1/8 full" people) - but over time the performance gradually improved beyond the best we'd been seeing with ad-hoc 95 filling - I guess the engine computer learns the better fuel.
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2015 (WK2) GC Limited 4x4 with Sprint Booster and Pirelli AT+ 275/55R20 Tyres (at STD height).
Last edited by Trailfirst; 05-04-2020 at 10:01 PM.
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