I use V-power - no appreciable change in mpg from normal but both my X-trail & CRV run smoother, quieter, seems a wee bit nippier........... all non-measurable by the punter.

30mpg for 9000miles = 300 gallons @ even 40p = £120.00 per year = £2.40 per week

With depreciation, Road tax, Ins, Servicing, tyres it is neither here nor there - the £2.40 won't buy a cup of coffee these days.

I did a test in my 2011 Volvo V60 D3 (163bhp) - a fairly modern turbodiesel with a relatively up-to-date common rail injection system and DPF.

I ran 10 consecutive tankfuls of nothing but Shell V-Power (i.e. about 6000 miles over 6 months using no other fuel), and compared with the 10 previous tankfuls of Shell's ordinary Fuelsave (easy for me to do, as Shell is my nearest filling station and is the same price as the local supermarkets).

So I did about 6000 miles in 6 months on 'ordinary' fuel, and then 6000 miles in 6 months on Shell's premium stuff.

I got a brim-to-brim average of 46.29mpg on V-Power compared with 45.12mpg on Fuelsave. At the time, V-Power cost 8p per litre more than the ordinary stuff.

Or, to express it in percentages, I got a 2.6% improvement in economy for spending the extra 5.7% cost of V-Power. I reckon that the 10 tanks / 6000 miles on each fuel was sufficient to reduce the influence of variables like ambient temperatures, type of journey etc. Please note I said REDUCE, not eliminate, the influence of variables, before people jump down my throat on this :)

There was no detectable difference in performance at all. I concluded that while V-Power might make a small difference to economy, it wasn't worth paying the extra for, compared with the ordinary, cheaper Fuelsave.

I have monitored mpg at each fill for extended periods, and have found no pattern of better economy with petrol or diesel (mainly diesel), using Shell/BP mainly.

The Shell and BP super diesel (I think Total Excellium has disappeared?) AFAIK are GTL based so inherently cleaner. The Esso one, from the blurb I infer, is just the claimed better additive package.

The benefit I would be after is just a cleaner engine and particularly diesel injectors, which could I suppose influence economy longer term.

The German company Aral developed BP Ultimate diesel. They did significant testing and on a Euro 3 diesel it was reasonably expected to give a 50% smoke reduction IIRC. It seems reasonable to think that cleaner burn (more complete combustion and less crud in the fuel in the first place) might have some benefit for DPFs and maybe EGRs - but I am not aware that anybody has made that claim.

There was also a claimed fuel saving of c 3%, but that is hard to see in the noise for most people I think.

I use the super diesel when I can get it, and when I can't I chuck some Millers in it, but that doesn't turn it into super diesel - it can't remove the crud from ordinary diesel, which is a simple distillation product of crude oil, but I think it does help stop the muck from gumming up the injectors. My subjective evidence for that is a Scorpio I once had, with the VM diesel boat engine, that smoked quite badly - Millers cleaned up the exhaust quite a lot, which I put down to cleaner injectors and a better spray pattern.

E&OE. I'm not a real petroleum chemist, but I knew a bloke who was, and he thought the Shell V-Power and BP Ultimate were worth the extra.

EDIT - just seen craig-pd130's post above. His 2.6% economy improvement is very much on the scale of the 3% assumption.

Edited by Manatee on 18/09/2014 at 13:07

using live data from my ecu I can measure a variety of variables. One of these is horsepower at the wheels, calculated from the vehicles acceleration and [known] weight.

On standard BP unleaded my maximum hp at the wheels is 208 at 5200rpm. On Shell Vpower it is 222 at 5400. before the nay-sayers start shouting me down, conditions were very similar (road, car load, ambient temp, warm up runs etc - testing was only a few days apart). I believe the improvement is larger than experimental error. The car is much better to drive, particularly in the mid range (it's forte is overtaking with 360Nm on tap from 2250 to 4000rpm)

on my regular run to work (on the M6/M42 over 45 miles each way), driving fairly consistantly gently over several tanks fulls, I have found an improvement of around 2mpg on VPower and about 1.5mpg on Ultimate.
Driving in the lanes tends not to yield any improvement in mpg, but the car drives much much better and I'm using the extra power.

My wife runs a C1. the car does the same journeys every week. On standard unleaded over several months it averaged 47 to 50mpg over tankfulls, only once touching 51mpg. A few weeks ago we started filling it with Total Excellium (available in our town) and the mpg is now typically in the 54 to 57 region.

So, I believe super unleaded (note that premium is the standard stuff) CAN improve the power or economy of a car, but results will be variable from car to car and how the car is driven.

I've done almost 30k in my car now and most of that has been on super unleaded. Looking down the plug holes recently it was obvious that the piston crowns are cleaner than they were soon after I got it. So longevity of the engine and it's performance is also likely to be enhanced by th euse of super. A desirable outcome for me, but not necessarily high on others priorities.

My last car an Automatic C3 would get an increase of fuel economy of about 4% using premium unleaded at at time when the difference in price was about 7%. I had more impact on fuel economy by driving economically when I could push it to about 46mpg from about 40mpg, but this involved driving no more that 55mph, basically driving like my Dad which was no fun at all,

The price difference between standard unleaded and premium (e.g Shell V power) locally is about 6%, so only worth the extra if mpg is increased by more than this amount.

Obviously some cars designed for higher octane fuel will go better, my question is not about acceleration/speed but mpg in normal driving.

Has anyone measured the difference (if any) in ordinary cars?

I've been looking into this recently. purchased a standard 1.2 corsa Petrol, 5 years old from a dealer with 25k on the clock. In the first 3 months of having it the best it managed was 260 miles on a full tank, 26mpg. This was all around town driving.

I thought to myself this is pretty rubbish for a small engined car, i expected more. Looked around online, looked into these premium fuels.

From all my research it seemed obvious Shell V Power Nitro + was the best quality fuel to put in your car for longevity of your engine and hopefully better mpg.

Also Tesco momentum 99 as a second choice.

Ive been trying the V power for 2 tanks, I ran the standard unleaded more or less empty to 1 or 2 litres and started filling up full tanks on the vpower.

I'm now getting 345 miles from a tank, an increase of 85 miles in a standard 1.2 engined car. To me thats excellent. To fill my tank up on v power just costs me £4 more so if i take that small cost into account im still gaining 60 miles on standard unleaded petrol and saving about £11 every time i fill up.

Forget about any negative opinions on Premium fuels, Any petrol car under 15 years can take them, take your car along near empty, fill up and drive the same as you always do, and see what you gain in mpg, i wasnt after a performance increase as its only a 1.2 corsa lol.

It does drive smoother though.

All cars probably react differently so see how yours does, im well happy, i'll be using V Power till i pop, I might try a tank of Tesco momentum 99 in a tank or two just to compare,

Happy driving Guys

As someone with a fair amount of motor trade experiance, my opinion is that Premium fuels are worth the extra depending on your vehicle. In my personal vehicle, a Citroen Cactus with the Puretech 82 engine fitted, it is not worth it. However, a friend of mine currently owns a large CC petrol engined 2004 Mercedes CLK in which his fuel econemy improved to 35 MPG and more from an averge of 22 MPG. Also, I was presented with a 2008 BMW 320i which belonged to a friend of mine which had several running concerns. Essentially the problems were all caused by using the "wrong" fuel. BMW did not demand to used a Premium fuel but it certainly made a huge difference in performace and fuel econemy and almost definintely is extending the life of the engine.

Also, the Peugeot Citroen EP range of engines, introduced in 2006, will require to run of the most premium fuel avaliable (even if it isn't demanded by the manufacturer) if you do not want it to write itself off within around 30,000 miles!

If your engine is at all inspired with perfomance, then YES use the premium fuels. Other than that it is trial and error really, give it a go and see how your car and MPG figures respond and decide from there. Just PLEASE do not use any of the fuel additives avaliable from Halfords!