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[Kevin Wood]

Somebody must have the facts.

How far can the ECU advance the ignition timing?

It doesn't. It retards it to protect the engine from poor fuel if it detects knock but won't advance it past whatever is mapped. I have never seen a datalog where knock retard has activated apart from when there's been a knock sensor issue.

Without a re-map, I don't think the Omega (certainly the V6's, not sure about the 4pots) will make proper use from higher octane fuels.

They are too mildly tuned for it to make much difference anyway, regardless of map. Also, with a  "pent roof" combustion chamber, maximum power is unlikely to be at the threshold of knock anyway. They just don't need that much advance. Increase the compression to 11.5:1 or turbo/supercharge it and you might start to benefit.

My 4pot B235R has been remapped to take (minimum) 98RON fuel.  It responds lovely to a dash of Tuloene, taking the RON upto ~101/102.  The difference is night and day.

That's forced induction, so a completely different beast.

[Broomies Mate]

Somebody must have the facts.

How far can the ECU advance the ignition timing?

It doesn't. It retards it to protect the engine from poor fuel if it detects knock but won't advance it past whatever is mapped. I have never seen a datalog where knock retard has activated apart from when there's been a knock sensor issue.

Without a re-map, I don't think the Omega (certainly the V6's, not sure about the 4pots) will make proper use from higher octane fuels.

They are too mildly tuned for it to make much difference anyway, regardless of map. Also, with a  "pent roof" combustion chamber, maximum power is unlikely to be at the threshold of knock anyway. They just don't need that much advance. Increase the compression to 11.5:1 or turbo/supercharge it and you might start to benefit.

My 4pot B235R has been remapped to take (minimum) 98RON fuel.  It responds lovely to a dash of Tuloene, taking the RON upto ~101/102.  The difference is night and day.

That's forced induction, so a completely different beast.

So, we can conclusively say, Super Unleaded is a complete waste of time on the Omega from a performance POV?    If it does nothing for performance, it can do nothing for economy?  Right?

I'm sceptical about the cleaning benefits of the higher octane stuff, or providing longevity to the engine.


So, once and for all (FOR THE OMEGA).  It's a waste of money, yes?

[omega2018]

in my old 2.5 V6  i did a test with super unleaded v unleaded.  same stretch of motorway every day, maintaining constant speed using cruise (out of rush hour) i got about 10% better fuel economy on the trip computer.

off cruise i 'm sure I got better performance but that was hard to measure.

never gone back to unleaded as super price is always less than 10% more

[omega2018]

super unleaded is normally 98 octane. normal unleaded 95.  owners manual page 216 says

"Octane requirement
unleaded 95
or unleaded 98 <sup>(2)

2)</sup> Knock control system automatically adjusts ignition timing according to type of fuel used (octane number)"

[Diamond Black Geezer]

Have to confess I think I've seen better economy. Now whether that's as direct as 'I get more miles per gallon from this super fuel' or more down to, without realising it I don't plant my foot as hard down in order to make the progress I wish, I can't say.

After months of leaving the trip as-is I decided to zero it before a long run. On the outward and return journey I got 30mpg, which has been steadily falling as I do 99% town driving, much, irritatingly short journeys where the engine just gets up to temp then I'm at work/home. I was returning 22mpg, dipping just under due to a few days of Heavy Foot Syndrome.

I'm now just at 24mpg, so let's see if she dips any further. If we return and settle out back at 22 then sadly that's making any economy benefits negligible. But it's been my belief that the super fuels are genuinely beneficial. Personally I'd say get Tesco only, however, as the cost vs benefits of Shell / BP don't outweigh the extra £.

[omega2018]

useful Tesco study "To assess whether Momentum99 delivers an improvement in fuel consumption across a range of popular used cars"
http://www.ttforum.co.uk/forum/download/file.php?id=115834&sid=9db90aa87ef3171de4a1ec24d4ca8687

average uplift in mpg of 6.2% using super over tesco's standard petrol.  some cars seeing 13% and 11% increase in mpg.

ethanol is another issue though, i have a suspicion tesco fuel has too much of it. 

[Diamond Black Geezer]

Good read. I wish, for a scientific study they'd said what vehicles were used. (they give the model, but that doesn't narrow it down that much - Ford Fiesta - is that a 1978 or a 2005 Fiesta?) etc...

Just trying to guess, really which of those test cars would best represent the Omegas results. The study shows the TT actually got a fraction worse using Tesco, the mean being 6.2%, but the maximum found looks to be about 13%, on a Golf 1.6.

It could well be that all the cars on that list were made long after the Omega was.

Interestingly, this report seems to suggest otherwise, and disagree with my observations, calling it a waste of cash...

http://www.thisismoney.co.uk/money/cars/article-1642366/Super-fuels-a-waste-of-cash-for-most-cars.html

read the article and they say there is a 'slight improvement' though they summarise in the title as calling it a 'waste of cash' which is typical misleading journalism, really. So what they're saying is that they do offer an improvement, however, only slight, in many cases. Ask an F1 chassis engineer what he's think to a 'slight' improvement in cornering and I know what he'd say. We already know that it's only ever a few %. Of course if you run a 75bhp Nova, then that's frankly irrelevant, if you drive a Veyron, then 3% is 36 bhp, and so on...


They also state that you could make more financial gains by altering your driving style. Well what a surprise! But saying that is only akin to 'don't invent seatbelts, just make people alter their driving style'  Personally my philosophy is if we wanted to do things on the cheap, we wouldn't be driving Omegas! 

[Mr Gav]

Ask an F1 chassis engineer what he's think to a 'slight' improvement in cornering and I know what he'd say.

Any improvement no matter how small is important in F1 as it is in any other motorsport but in a two tonne barge it`s really not that critical

We already know that it's only ever a few %. Of course if you run a 75bhp Nova, then that's frankly irrelevant, if you drive a Veyron, then 3% is 36 bhp, and so on...

Even 36 bhp wouldn`t be noticable in a Veyron 

They also state that you could make more financial gains by altering your driving style. Well what a surprise! But saying that is only akin to 'don't invent seatbelts

You can`t really compare being a bit lighter on the throttle to not inventing the seat belt 

You can alter your driving style and get better returns than buying expensive fuels, it defeats the object of getting more mpg if you`re paying more.

[Diamond Black Geezer]

Hear what you're saying  My point was that the article suggests instead of using a technological improvement, we should alter our habits instead. This, as with any study or experiment is adding a variable, which makes the very concept and point of the test a little moot. Ok, fair point, comparing seat belts to fuel octane may appear extreme, but whatever the example given, the point remains, ie:

My criticising of the article's construction was they were saying 'we investigate if abc gives more energy than xyz. We find, well, yes, it does; however, you could save using abc or xyz by using less in the first place.' Well, yes, quite right, but the question was not 'if we use less stuff in the first place will there be less stuff used?', the question was 'does abc give us more energy than xyz'


But, fair enough. I pose a further question, therefore. If we were her on OOF to unanimously agree that £ per mile, a 'super unleaded' in fact offers less bhp-per-£ than regular unleaded, given the actual higher quality of the super unleaded fuel, proven benefits to engine life etc, who is still willing to use it? Akin to buying organic vs cheaper import tomatoes for your pasta sauce...

[Mr Gav]

People probably alter their driving styles without even realising it when they put in a fuel they think will give them more mpg and then bingo all of a sudden they are getting more mpg but give it a few weeks when they settle in the old routine the mpg drops, a bit like the placebo effect, also why people think they get more power too 

[Broomies Mate]

in my old 2.5 V6  i did a test with super unleaded v unleaded.  same stretch of motorway every day, maintaining constant speed using cruise (out of rush hour) i got about 10% better fuel economy on the trip computer.

off cruise i 'm sure I got better performance but that was hard to measure.

never gone back to unleaded as super price is always less than 10% more

I'm an advocate of higher octane fuel, but 10%?? You are off your rocker!

[Diamond Black Geezer]

Hmm... 40mpg to 44, which seems a old fair jump.. then again I'm returning (at present) 23.3 mpg, vs 22mpg since before the oil change, and about 21mpg when I was on Asda's finest. So that's 21 to 23.3 which is 2.3 mpg = 10%.

I openly admit there was an oil change in that, too. And it's possible my mpg will fall, still; though it's settled at 23.3 for the last few days. (mind, the extent my display is out of pixels, it could be 28.8, haha!  )

As Gav says, the placebo effect is in there, as is overall driving style, and we've no way of truly, removing that. Literally all I can think is actually having an engine on a bench, or taking it round Millbrook on a specific set of test routes and speeds. (as was done in the above report) I just wish we'd had more technical data of the vehicles used. 'Ford Fiesta' really does cover a fair few vehicles! This effect of whether or not the V6 can or can't, and what other engines can - and can't - take advantage of the knock control does grate, as it's an issue.

I do, pretty regularly, fill up just once a week - but here's the catch.. I don't fill up by litres, I fill up by £s so when I was putting in £25 of derv in the Turbo Weasel, when I started putting in £25 of Asda cheap n cheerful, and then £25 of Tesco Optrex, that's the point, in theory, given the higher cost of the Tesco Superfuel, I am getting slightly less litres, and yet am covering about the same miles. That means, theoretically, more mpg. Perhaps any extra miles gained is offset by the extra cost, but nevertheless, the higher quality of fuel going in in the first place does give me a satisfied feeling.

Same feeling as knowing my wishbones ball joints are genuine Vx. The car doesn't perhaps appreciably drive any better, but I know I'm using quality. 

[Mr Gav]

If you`re happy paying the extra and believe that you`re getting better mpg then go for it, personally I don`t think we see the benefit in these older cars so I just stick with Shell`s standard stuff, I`m really not bothered about how clean it keeps the insides of the engine as it has already done 146k.

I used to run Shell V-power in my Senator that I used to commute up to Catterick  Garrison and didn`t notice any difference in mpg or power over the course of a few months so I went back to the cheap stuff and saved a few quid 

Now if I had a newer car, say five years old then it would be a different story 

[Diamond Black Geezer]

Oh, totally. 

I ran on Asda for several months without really noticing much, and at best any difference in only negligible. I think because I'm on this for the 'long haul' - I have no intention of ever getting rid of my Omega - that I try and get the best quality for long-term benefits where possible.

 

[omega2018]

in my old 2.5 V6  i did a test with super unleaded v unleaded.  same stretch of motorway every day, maintaining constant speed using cruise (out of rush hour) i got about 10% better fuel economy on the trip computer.

off cruise i 'm sure I got better performance but that was hard to measure.

never gone back to unleaded as super price is always less than 10% more

I'm an advocate of higher octane fuel, but 10%?? You are off your rocker!

why don't you just try the test instead of spouting off with no experience?

cruise control on the same stretch of motorway a few times is a way of removing the placebo effect.