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      09-21-2020, 01:01 PM   #1
dragonsdreams
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Worth using high octane fuel?

Hi folks, has anyone compared performance of the different octane rated petrol/ gas in their i8 and thinks it makes a difference?

I see in the UK that Tesco do a 99 RON fuel (Momentum 99) which is supposed to give about 6.5% increase in bhp and 14% better fuel economy over Tesco's standard unleaded...(Autocar)

When I had my Cayman I can't say I noticed any difference between standard RON 95 and Shell V power.🤔
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      09-21-2020, 02:00 PM   #2
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You may not notice the difference but your engine will. Using a low octane rated fuel in a high compression, turbo charged engine will cause pre-ignition and damage your engine.
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      09-21-2020, 03:07 PM   #3
dragonsdreams
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Quote:
Originally Posted by Coastal i8 View Post
You may not notice the difference but your engine will. Using a low octane rated fuel in a high compression, turbo charged engine will cause pre-ignition and damage your engine.
I guess what I meant was has anyone tried the RON 99 against the more common super unleaded which in the UK is RON 97. Ordinary unleaded is rated at 95.
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      09-21-2020, 04:02 PM   #4
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The engine map is optimized for the recommended fuel. You can use higer Octane numbers with homeopathic increase in performance and decrease of consumption, not at all justifying the price premium. You can have the engine mapping changed to higher Octane numbers with more effect but also with the downside that you can damage the engine with lower Octane fuel. I also expect in the i8 the interaction of electric and ICE, etc. make this a futile exercise.
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      09-22-2020, 06:00 AM   #5
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In the US, we are required to use 93 octane in the i8. I purchased 100 octane for testing.
These are 98 and 105 RON. I did 0-60 testing on both and noticed no change in performance.
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      09-22-2020, 09:31 AM   #6
dragonsdreams
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Quote:
Originally Posted by patsgarageonline View Post
In the US, we are required to use 93 octane in the i8. I purchased 100 octane for testing.
These are 98 and 105 RON. I did 0-60 testing on both and noticed no change in performance.
Worth knowing, thanks Pat.
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      09-23-2020, 01:50 PM   #7
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High octane fuel

As noted by others, the difference in performance might be marginal as the engine knock sensor will compensate for the lower octane fuel. The more important factor in my experience is the amount of ethanol in your fuel. After some research and personal experience, I would never put any amount of ethanol through my high output little engine. I have seen the results of ethanol on fuel tanks and systems. Storage is a big issue as well. Even with fuel stabilizers, corrosion from ethanol even in small amounts is bad. I recently drained the unstabilized 20 year old "premium" fuel from my Rolls Royce. Just for entertainment, I filled the fuel bowl and put the fuel pickup line on my 1974 Nissan pickup into a one litre container of my old fuel. To our amazement, the engine flashed up with no hesitation and sat idling away smooth and happy! Perhaps sitting in a vintage Rolls Royce was a privilege for the fuel, but in any case the fuel was unleaded and un "corned" - There you have it. PS. The old fuel is being used up in the lawn tractor and the Roller is getting fresh un-ethanolled premium 94 (Canada).
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