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Kurt Barlow

Unleaded V Super Unleaded (Fuel Efficiency)

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I occasionally fill our 2.0L Nissan Qashqai with 98 octane Shell V Power v standard 91 octane. We always seem to get much better fuel economy. We get approx 650km on a tank of 91 v 750-800ish on 98.

The ride seems a bit quieter and smoother too.

The extra cost is probably not covered by better economy but the difference is clearly there.

However whenever I read motoring press reports they claim no fuel economy advantage from using higher octane fuels.

I wondered what other posters findings / views are?

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I have a 2L civic type r (probably not the right car for fuel economy) and i have been keeping a record on mpg over the past 6 months. I have found that on std shell unleaded i average 38 mpg whilst on supermarket fuel the average is 34. Now if i bye the high octane stuff, which my car is unable to utilize to its full potential, i get nearer 40 but i've only bought a few tanks of this so it probably isn't a very representative result. However, i am certain that on supermarket fuel i get ~10% less mpg than when i use fuel from a premium garage.

My driving routine is typically two fifteen mile trips per day which is 50% B road and 50% stop start driving. On a motorway run at 70-80 mph i get typically 38-43 mpg whilst on a bit of rapid driving the mpg drops to 28 ish. Interestingly i had a 1.8 petrol focus which produced 32 mpg even when driven like a nun.

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Given that the V Power and the BP Ultimate are both supposed to be alcohol free you should get a little bit more MPG. In addition, a turbocharged engine with a decent management system should be able to take advantage of the higher octane of the V Power and BO Ultimate and use a bit more spark advance and/or a bit more boost depending on whether mor power or better economy is mapped for that particular combination of parameters.

Whether or not it pays in terms of economy will be different for every user.

It is wort bearing in mind that the various seals in the fuel system in older cars can degrade when exposed to alcohol especially if seldom used. For that reason alone my wife's 15 year old Ka always gets the good stuff.

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I have a 2L civic type r (probably not the right car for fuel economy) and i have been keeping a record on mpg over the past 6 months. I have found that on std shell unleaded i average 38 mpg whilst on supermarket fuel the average is 34. Now if i bye the high octane stuff, which my car is unable to utilize to its full potential, i get nearer 40 but i've only bought a few tanks of this so it probably isn't a very representative result. However, i am certain that on supermarket fuel i get ~10% less mpg than when i use fuel from a premium garage.

My driving routine is typically two fifteen mile trips per day which is 50% B road and 50% stop start driving. On a motorway run at 70-80 mph i get typically 38-43 mpg whilst on a bit of rapid driving the mpg drops to 28 ish. Interestingly i had a 1.8 petrol focus which produced 32 mpg even when driven like a nun.

I was working for a Pub Co in 2009-10 and did a lot of travel around the South East in a 1.8L Avensis. I always used to try and fill up at a Shell station near St Albans. Fuel at Supermarket prices but without the corresponding mpg drop which I noticed with supermarket fuels especially Sainsbury.

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Given that the V Power and the BP Ultimate are both supposed to be alcohol free you should get a little bit more MPG. In addition, a turbocharged engine with a decent management system should be able to take advantage of the higher octane of the V Power and BO Ultimate and use a bit more spark advance and/or a bit more boost depending on whether mor power or better economy is mapped for that particular combination of parameters.

Whether or not it pays in terms of economy will be different for every user.

It is wort bearing in mind that the various seals in the fuel system in older cars can degrade when exposed to alcohol especially if seldom used. For that reason alone my wife's 15 year old Ka always gets the good stuff.

Ours is the 2.0 Litre unit they stick in Aussie Qashqai's. We don't get the suped up Micra 1.2L the British get treated to....

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Ours is the 2.0 Litre unit they stick in Aussie Qashqai's. We don't get the suped up Micra 1.2L the British get treated to....

If there is a British 1.2 Micra I'd bet that there is a 1.0 for the Irish market. :)

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I try to put premium fuel in my 1.6 Focus where possible.

Despite what i read online about it being a waste of time in such cars, i feel a notable improvement in smoothness at the lights. Its definitely more responsive.

My particular model has a "hesitation" that im told is part of the design on this engine. Better fuel seems to take the edge off of that.

I aim to keep this 7 year old car (owned from new) for yonks so i figure a better fuel may help with valve seat burn and so forth. Not really been keeping an eye on the MPG as i do mainly pootling and hospital runs with old man at the minute.

V Power seems to be the best and round my way is far cheaper than the Esso equivalent.

I used Tesco Momentum which is a notch higher at 99, and my car ran like a tank. Dreadful stuff.

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From what I've read for most engines it shouldn't make any difference, so you're just wasting your money. At least as regards the higher octane rating. If there is a difference in performance (whether power or efficiency) it makes me wonder what else is different.

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I occasionally fill our 2.0L Nissan Qashqai with 98 octane Shell V Power v standard 91 octane. We always seem to get much better fuel economy. We get approx 650km on a tank of 91 v 750-800ish on 98.

The ride seems a bit quieter and smoother too.

The extra cost is probably not covered by better economy but the difference is clearly there.

However whenever I read motoring press reports they claim no fuel economy advantage from using higher octane fuels.

I wondered what other posters findings / views are?

Ah! You're in Australia - I was wondering where you were getting the 91 Octane from.

I'm sure you'd see a noticeable difference going from 91 to 98. The engine will be able to put in quite a bit of advance and get more power out (or, you can have lower throttle openings for the amount of power you want).

I remember once filling with 2* (about 91 RON) by mistake and the engine ran like a pig - I was only a poor person then and had put £5 in (well, a 1/4 tank, say) - things improved markedly when I mixed in some 4* (about 98 RON). But then that was an old-fashioned car with no ability to move the ignition point, and was set up for 4*.

But I'm not sure there is that much difference between 95 (equivalent to 3*) and 98. I can see it on a performance car but it is fairly subtle, while for regular car journeys I really don't see any difference, in power or mpg.

[but I would accept that most of my cars are just too old - I've tried it on the ones with electronic ignition (pointless on a car with a distributor*) but I'm not sure that they're doing all the knock sensing stuff]

*feeling pleased with myself for that one.

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Isn't it an absolute pisser when you put the super in by mistake, since I doubt it makes any difference. It doesn't help when you have choice between super duper and super premium.....which is the cheaper one.

As for fuel efficiency it depends on how you drive, brake and the speed you are travelling at. Optimum on my 107 is slow, about 37 mph where by the car is driving with barely the aid of the gas pedal...so if I have a holiday on minor roads I can get about 90 to the gallon, down to about 45 motorway driving.

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Isn't it an absolute pisser when you put the super in by mistake, since I doubt it makes any difference. It doesn't help when you have choice between super duper and super premium.....which is the cheaper one.

Depends on your car. Mines mapped for 99 RON so I only ever use Momentum. Some stations advertise it but don't supply it. Car runs like crap on 95 :(

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You have to modify your driving style to take advantage of the premium fuel's differing characteristics.

It burns better at lower rpm, so allows you to shift up earlier and use a higher gear than otherwise. I think this is mostly where the fuel savings can be achieved.

Apparently more even burning reduces hot spots and has knock on benefits for longevity of the engine.

I noticed around a 10% uplift in economy in my wife's old Euro II Corolla, compared to branded regular fuel (typically She'll vs She'll Vpower). This was definitely not an engine optimised for premium. Subjectively the engine also seemed to run smoother.

The bare mpg uplift did not in itself justify the premium, although at higher prices the case improves. The unknown is to what extent running a cleaner engine reduces ongoing maintenance and repairs in future.

I only use super when available, to disclose my habits. I avoid supermarket fuel entirely unless exceptional circumstances arise.

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As for fuel efficiency it depends on how you drive, brake and the speed you are travelling at. Optimum on my 107 is slow, about 37 mph where by the car is driving with barely the aid of the gas pedal...so if I have a holiday on minor roads I can get about 90 to the gallon, down to about 45 motorway driving.

Bimbling along minor roads is far more pleasant than belting up and down the motorway anyway, even if it take a lot longer (not that stops me being annoyed if the bimbler is in front of me). Where possible try to just enjoy it and not worry about the time.

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Bimbling along minor roads is far more pleasant than belting up and down the motorway anyway, even if it take a lot longer (not that stops me being annoyed if the bimbler is in front of me). Where possible try to just enjoy it and not worry about the time.

Yep in N Wales at the moment....Ashbourne, Stone, Whitchurch, Llangollen, Horse Shoe Pass, single scenic carriageway minor roads getting 90 to the gallon and places to stop en route. Anything to avoid the God forsaken roads of Cheshire around Nantwich and Crewe or north via Chester. God knows why Cheshire is so posh.

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Honest John swears by it so that's good enough for me. Makes me feel superior to plebs who can't afford the premium price. As well as MPG I read it can have detergent like additives which may help with engine cleanliness, issues with choked up areas etc. I know nothing about engines so this could be cobblers.

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You have to modify your driving style to take advantage of the premium fuel's differing characteristics.

It burns better at lower rpm, so allows you to shift up earlier and use a higher gear than otherwise. I think this is mostly where the fuel savings can be achieved.

Apparently more even burning reduces hot spots and has knock on benefits for longevity of the engine.

I noticed around a 10% uplift in economy in my wife's old Euro II Corolla, compared to branded regular fuel (typically She'll vs She'll Vpower). This was definitely not an engine optimised for premium. Subjectively the engine also seemed to run smoother.

The bare mpg uplift did not in itself justify the premium, although at higher prices the case improves. The unknown is to what extent running a cleaner engine reduces ongoing maintenance and repairs in future.

I only use super when available, to disclose my habits. I avoid supermarket fuel entirely unless exceptional circumstances arise.

Interesting - thanks. This may explain the observed improvement in MPG and vehicle ride.

My wife does 90% of our driving as she uses the car for commuting so I doubt any change in driving style for one fuel type to another.

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I've never tested it scientifically, but I do reset the average MPG on my car's trip computer most trips and see how it does. Never noticed any difference at all in the MPG or the way the car drives between supermarket and branded fuel. That said the supermarkets really aren't much cheaper any more so I try to buy Shell fuel if I can. Also the car is a 200bhp 3L V6 so I very rarely need to use more than 1/4 throttle in normal driving, so never come close to conditions where the engine is in danger of pinking.

As others have said, the octane rating of the fuel should only make a difference if the car is using a knock sensor to optimise the ignition timing (and in the case of a car with forced induction, the boost pressure). I wouldn't have thought that many naturally aspirated engines run a high enough compression ratio that 95 octane is marginal; 91 octane might well make a difference, but they don't sell it over here. It depends whether it's MON or RON too apparently, stuff sold as 91 octane in the US is apparently equivalent to our 95.

If supermarket fuel has ethanol in it then you would expect a small reduction in economy as it would contain less energy by volume. However if it's 10% ethanol that should equate to about a 3.5% difference, or 33 vs 34mpg...

http://www.afdc.energy.gov/fuels/fuel_comparison_chart.pdf

Ethanol actually has a very high octane rating, I think Tescos Momentum 99 gets its high rating from having a lot of ethanol in it, so you would expect it to be crap for economy. If supermarket fuels have 10% ethanol in them and still only manage an octane rating of 95, then I guess the fossil fractions they're using to make up the rest of it must be pretty crappy stuff.

E85 seems to have gone off the radar recently, but if you can find somewhere to buy it, and it's cheap enough, then it's great for running turbo cars on as long as the fuel system can take it. A few years ago a chap in Practical Performance Car magazine (Dave Walker of Emerald) fitted one of his own ECUs to a 924 Turbo and mapped it up for E85, and it made great power. Edit: obviously you need enough injector capacity to squirt it all in, as the stoichiometric ratio is about 9:1 as opposed to 14:1 for petrol.

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Interesting - thanks. This may explain the observed improvement in MPG and vehicle ride.My wife does 90% of our driving as she uses the car for commuting so I doubt any change in driving style for one fuel type to another.

The poster koala_bear had good knowledge on this stuff, ages ago though. It seemed like he/she is in the industry so a good source. As noted above, "Honest John" is a long-time fan. The premium stuff produces more power and torque at a given rpm than standard.

I guess it's partly about safely minimising the number of revolutions your engine performs per mile in order to increase mpg.

Wouldn't surprise me if motoring hacks do comparisons at a freebie track day or similar, and don't see any mpg difference but maybe note a performance uplift instead. Guess, as with hybrid cars, the extra output can be used either as savings or as a performance enhancer.

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My 1987 Honda motorcycle loves the decent fuel, you can tell the difference when riding.

I don't measure mpg so couldn't say about economy.

Ah. That's old enough that it will have been set up for 4* petrol. 'Premium' unleaded is more like a poor 3*.

As your bike (probably) won't be able to detect knock it won't retard the ignition for the poorer fuel. If you did retard the ignition you'd possibly find it ran a bit smoother on 95, but you'd suffer in power and mpg.

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My car (Clio 2.0 16v non-turbo) is supposed to run on 98 octane. I can't tell any difference between ordinary petrol and premium when it comes to mpg or power. I run it on standard 95 stuff these days. The same goes for every car and bike I've ever owned, even a blackbird and a zx12r. It's a different story if your car is highly tuned or has a turbo. Most new cars are turboed these days so in theory they can run higher boost and more advance on premium fuel. That should give them more power and better economy depending on how you drive.

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My 1987 Honda motorcycle loves the decent fuel, you can tell the difference when riding.

I don't measure mpg so couldn't say about economy.

you can definitely tell the difference with bikes.

on my little 125,I can get over 100mpg on both quite easily,but for standard supermarket 95RON petrol I'm hard pushed to get it much above 60mph.

with 98RON (either BP ultimate or V-Power), it will get up to 70.,and you can really tell the difference in "pulling power" on the throttle.

for the sake of 30p extra a fill it's well worth a tank of the good stuff.

realistically feels like an extra 10%BHP

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Ethanol actually has a very high octane rating, I think Tescos Momentum 99 gets its high rating from having a lot of ethanol in it, so you would expect it to be crap for economy. If supermarket fuels have 10% ethanol in them and still only manage an octane rating of 95, then I guess the fossil fractions they're using to make up the rest of it must be pretty crappy stuff.

The legal maximum for ethanol is 5% which also happens to be exactly what the EU roadfuel biofuels target is. The result is that essentially all road petrol sold in the UK has 5% ethanol. There is a slight discrepancy between the amount of ethanol and the amount of oxygen. A maximum of 2.7% oxygen is permitted in petrol, but 5% ethanol corresponds to about 1.9% oxygen, so it is not uncommon for additional oxygen, typically in in the form of ethers, or occasionally methanol to be added to bring it up to 2.7%, for reasons of emissions.

In practice, there is no difference in oxygen content between 95 and higher fuels, other than the refiner's internal policy. For fuel purchased on the spot market (pretty much all 95 unleaded), this is whatever the supplier has in their tanks. For high octane fuels, these may be prepared specially by the refiner - although one of the largest broker/dealers, greenergy, can generally supply 99 RON on the spot market (which it supplies to Tesco as Momentum 99).

Greenergy helpfully provide periodic analyses of their fuel batches on their website, so you can see what the specifications of the fuel being supplied is. As you might expect as a dealer, it fluctuates wildly, but within the legal requirements.

The key difference between the high octane fuels and 95, is in the base fuel. The ethanol blending does allow a lower octane rating for the base fuel. In the case of 99 RON fuels, the base fuel is different, and contains a higher concentration of reformate, which is rich in aromatics and olefins, both of which have extremely high blending octane numbers. There is also a second quirk of this; olefins and aromatics have a higher carbon:hydrogen ratio by virtue of being unsaturated, and therefore produce a denser liquid fuel (99 RON is approx 3.5% denser than 95 RON), although this is partially offset by the lower LHV of aromatics (accouting for a gravimetric reduction in energy density of approx 1% between the two fuels).

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