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Discussion Starter #1
So I'm on my 3rd tank of Shell 95 after almost exclusively using V Power 99 on my 19 Veloce. The car is just not as responsive and tbh I'm surprised by how big a difference there is.

Ultimately, the car is pretty much as quick as usual, but it just doesn't come on full boost (seat of the pants measurement btw) as quick. It's really noticeable on manual shifts. When running V Power the shifts are really aggressive due to almost instant full throttle immediately after an up shift.

On the standard stuff there is a noticeable delay before getting full throttle. I'm also convinced there is less induction noise on 95 Ron.

One thing to point out is that it seems to have taken a couple of tanks of standard petrol for this to become apparent.

Anyone else with a similar experience?
 

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I almost always fill Shell V power over the 30k miles and 3 years. The handful of times I have been away and had to fill lower octane fuel, I have noticed a change in responsiveness and how powerful , smooth the engine felt after a couple of tanks once the ECU has adapted to the fuel. Our Giulia engines have a high compression ratio, IIRC 10:1. Higher octane fuel helps resist knocking, some modern ECUs adjust fuel maps and timing based on the fuel so that could mean with the lower octane fuel it is altering spark timing and hence power perhaps?

So yes what you feel is quite real. Although going too high an Octane or running race fuel won't benefit much as the ECU will just pull things back I suppose. The additives in V Power probably also help with the engine smoothness.
 

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yes big difference in feel I use tesco 99 and it almost feels like the difference between N & D over 95
 

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Discussion Starter #4
I know there is some scepticism about the benefits of using higher octane fuels but the difference is surprising actually.

I'll be going back to V Power, make the most of the lower fuel prices!

I wonder if it is just the timing that is pulled back on 95 vs 99 or if boost is effected too.
 

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Pretty much exclusively use V Power in my QV and both Harleys. (y)
 

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I know there is some scepticism about the benefits of using higher octane fuels but the difference is surprising actually.

I'll be going back to V Power, make the most of the lower fuel prices!

I wonder if it is just the timing that is pulled back on 95 vs 99 or if boost is effected too.
My understanding is, if the ignition is retarded by the ECU you lose some power so the ECU will have slightly lower boost demand. Boost is closely controlled by the feedback loops from the sensors that feed the ECU so it would be safe to assume that I think. It could also be that peak boost is still the same but occurs slightly later giving the feeling of laggy response and less power?
 

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Discussion Starter #7
My understanding is, if the ignition is retarded by the ECU you lose some power so the ECU will have slightly lower boost demand. Boost is closely controlled by the feedback loops from the sensors that feed the ECU so it would be safe to assume that I think. It could also be that peak boost is still the same but occurs slightly later giving the feeling of laggy response and less power?
Yeah I agree. Peak power probably isn't effected too much. But the power probably is coming through quicker
 

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It seems the additive is poured into the underground tank at fuel station delivery time from what I’ve read. If so it’s a shame you can’t buy that magic ingredient for when you can’t get to the Shell station. I used to use the premium stuff in my Giulietta MA and although I’m not sure if the same effect is possible with diesel the Stelvio generally gets the premium stuff.
 

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I’ve used the Millers additive in the diesel when I couldn’t get vPower. Oddly it has the same smell and had the same effect. Haven’t tried the petrol version yet though.
 

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Pretty much exclusively use V Power in my QV and both Harleys. (y)
I never bothered with high octane fuels before getting the Quadrifoglio, but I'm in no doubt that such a high performance engine deserves it. I almost exclusively use VPower. Having a Shell station within half a mile of home is a factor.
On the rare occasions I had to use 95 octane, because I've got a near empty tank and no high octane pump nearby, I've put in no more than 20 litres and filled up with high octane at the first opportunity. So I've no real understanding of how less well the Quadrifoglio runs on ordinary fuel. In any event, it's not very often in a Quadrifoglio that one can use full throttle and notice any difference.
 

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If your engine is designed to run on 99 (or at least has the ability to advance the ignition to take advantage of it)....and Im guessing a Quad would be!!....then of course you will feel an advantage. If you have a run of the mill petrol car that has been designed and optimised with 95 ron in mind then it wont be able to take advantage of the higher octane juice....it will only be able to retard the ignition if you put some lower octane/quality fuel in....like if you drive abroad you can fine fuel lower than 95.....not advance it for higher octane. If you car was designed with 95 in mind than running 99 in it is just cash out of the exhaust
 

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Sounds like your having a great time experimenting whilst the roads are empty - they are empty for a reason though
 

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Since I collected the car last year from the dealer and just ticked over 20K now since last May I have only ever (bar maybe one occasion where I have been on fumes) used VPower and like Andy I have a Shell station half a mile away. I wouldn't use anything less to be honest.

I do get a fair bit of stick off my work colleagues though who argue there is little to no difference between the 95 & 99 fuels. I would argue that maybe on a 5 year old car with 80K on the clock you may not notice the difference if you fill the odd £20 worth of RON99 on occasion, but on a performance engine from new and where the manufacturer advise using RON99 I would always go with RON99.
 

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Sounds like your having a great time experimenting whilst the roads are empty - they are empty for a reason though
I am not sure why the dry sarcasm which I am guessing is aimed at the OP. The OP has only asked a question based on his experience of change in fuel. No where has his post suggested he is driving around just for fun. He may be a critical or essential worker. These may be his observations over previous journeys. I am a critical worker in the utility industry and I am working partly from home and partly on site. So some of us do have to drive to work. Nothing is stopping you enjoying your essential journey is there? Especially when everything is doom and gloom, as long as we are responsible. Think all of us here are mature enough to understand why the social distancing and unnecessary travel restrictions have been imposed.
 

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I have it from reputable tuners that our ECUs are capable of advancing ignition for higher quality, Octane fuel. Of course there are limits like I mentioned in my first response.
 

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Discussion Starter #16
Sounds like your having a great time experimenting whilst the roads are empty - they are empty for a reason though
I'm sure I'm still allowed to give it full throttle on my usual commute to work where appropriate.

And before you ask, my work is officially "essential" and I can't work from home.
 

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Discussion Starter #17
As for the difference between fuels, there is a definite distance, that I can feel, between the 2. But it could be placebo. A car that can do 0-60 in 5 secs though is not what I would class as "run of the mill" . It's a fairly high performance engine for what it is.
 

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If you car was designed with 95 in mind than running 99 in it is just cash out of the exhaust
There was a time when I thought the same, but had to put some cheapo unbranded fuel in my MX5 a few years ago and it was so rough that I filled up with BP Ultimate (97RON) ASAP to cancel it out and have stuck with it ever since (my nearest station is BP), sometimes using Shell 99 if I am away from home. I also use 97 full-time in my Giulia Veloce. I don't do enough miles to worry about the extra cost, but the MX is definitely smoother and will pull more cleanly from low revs (when I'm that way inclined). I had a similar experience when I had an Alfa GT some years ago and ran it for a while on 97 - it was definitely smoother than on 95.
I can't really compare 95 vs 97/99 in the Giulia as I've never fuelled it with anything other than 97 minimum.
 
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