Try Sainsburys' My last fill up was about 3 weeks ago and I chose the higher octane as it wasn't crazy prices.

Indeed - the supermarkets, and (to me, anyway) Sainsbury's in particular, have the lowest 95Ron to superunleaded price differential, normally somewhere between 5p and 6p a litre, and as the supermarkets offer the cheapest regular fuel anyway, the gap between their superfuels and the branded filling stations is often 10p a litre.

That being said, Sainsbury's superunleaded is 'only' 97Ron, where as Shell's is 98 or perhaps 99, as are all the other branded ones. I think Tesco's in 99Ron but may have a higher content of biofuel - not sure.

The main claim of the branded filling stations' premium fuels is that they have significant amounts of cleaning agents in these fuels (some in their regular fuels, again, more than the supermarket equivalents) that are supposed to help clean/keep clean (much freer of carbon deposits) the engine, intake valves, fuel injectors and exhaust/emissions systems, which also improves mpg and reduces emissions, as well as prolongs the life of these components. As well, of course, as improving performance on 'most' cars equipped with knock sensors.

HJ swears by the branded superfuels for the cleaning abilities specifically and regularly recommends them, though only, as the OP says, when the price differential is (in today's prices) 10p a litre or below. Unfortunately that price differential is getting wider, especially as many branded filling stations don't appear to want to compete on price with the supermarkets for their regular fuels any more.

I've seen price differentials between Ron 95 supermarket fuel and Shell V-Power of 20p a litre. I might treat myself and buy it (I still check to see where its cheapest, even amongst branded/Shell filling stations before buying) when I go on holiday to the West Country (up to 1000 miles during the time away including travel to/from the area), but not outside of that.

I now will just buy (when on offer) a bottle of Redex or other quality brand fuel or exhaust system cleaner which appears to do the same job at a fraction of the cost (one 4 dose bottle can often cost the same or less than the cost difference of a fill up with V-Power over regular) for seemingly a very similar outcome.

The effects of the higher octane/branded superfuels may be much more pronounced for more modern and/or higher performance cars (especially turbocharged) than my standard 12yo Mazda3, and because mine doesn't get gunked up as I don't use it for short journeys.

I tried Sainsbury's superunleaded for a while and noticed no discernable increase in either mpg or performance; a small increase (about 3-5% [1-2 mpg] - this could've been due to weather) in mpg when using V-Power or Redex over 4 fill-ups - presumably it cleaned the injectors etc a bit (which were probably quite clean to start with).

My local filling stations tend not to sell superunleaded or have it on one pump only . Must check Sainsburys again next time I visit. The Esso garage in Buxton run by Tesco. had superunleaded on every pump.

Thanks for your inputs.

I spent £524 for a BIG service at my Indie about 5/6 weeks ago

He flushed the engine oil + flushed the fuel lines. New ATF in the autobox..

I have noticed the car is "nippier" (not fast but an improvement).

The car is 6 years old & has been run on Shell V-power mostly - of late very little Shell as the 15/16p margin in my area was too strong for me. Still fill it with Premium however.

Smoother, nippier, MPG is still 30 - no improvement.

Some cars, like my Octavia 1.4tsi, have adaptive valve timing and can, by design, get better mpg and more power out of higher octane fuel. But I usually run on the regular 95 octane. When Honest John himself praised the higher octsne fuel, under certain circumstances, I went looking for it. Probably not use it again due to the higher price.

Therein lies the sticking point. Certain engines (seemingly turbocharged ones with reasonably high power outputs) benefit more from higher octane fuel, at least tangibly.

My Civic 1.8 has been running absolutely fine and sees no benefit from higher octane fuel.

Indeed - because its advantages seem to vary quite a bit in raw mpg/performance terms from engine to engine and make to make, and because well maintained, sympathetically driven standard cars are in better condition generally, there's a significant disparity achievements.

For my circumstances, the extra cost (even when it's as low as 6p a litre) is just not worth it on an ongoing basis, as the performance boost isn't there (noticeably) and the mpg increase was minimal, and no more than using the cheaper injector cleaner or similar quality additive. For others with different cars driving under different circumstances, then it may be, including the use of branded fuels with high levels of cleaning agents.

I think that some of the branded filling stations are effectively pricing themselves out of the market (e.g. Shell) by charging so much more for their superfuels. Two local Shell filling stations recently changed over to BP and Esso, and lo and behold are now selling their version of V-Power for a reasonale amount less than they did under the Shell banner - quite surprising, as in the past (10+ years ago), I always found that BP filling stations, especially out-of-town ones, were always the most expensive of the branded filling stations.

I just (Tuesday) filled up with Ron95 from the unattended Asda filling station in a nearby town when I was shopping there, and it was between 17-20p a litre more expensive to buy branded superunleaded - that's an extra £9.35 - £11 per tankful! Ouch!

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Edited by RT on 03/11/2018 at 09:26

There really can’t be many cars that require superunleaded,

My previous BRZ required it for full performance (98+ on the fuel flap) and my current Superb also states the same on the cap.

My understanding is there are three reasons for superfuels....

1. Better m.p.g. I did a brim to brim test of over 1000m on super 97 or 98, followed by over 1000m of supermarket 95. With super, mpg was less than 5% better but the extra cost was nearer 10%.

2. Better engine cleaning. All fuels, even cheap 95, contain additives and detergents to keep the injectors and engines 'clean'. Thanks to modern engine management systems engines haven't needed decarbonising for decades. I now firmly believe that using superfuel for better cleaning is a bit like using two squirts of Fairy liquid instead of one - the dishes will emerge just as clean. I, and I suspect many others, have run engines to over 200,000m without any problems on the cheapest fuel available.

3. Optimum power. Audi recommends either 98 or 95 RON for my car, advising that slightly less power will be available if using 95. Not an issue for me, so I'm sticking to supermarket fuel.

V power was 10p a litre more than regular at my local Shell when I called in yesterday.

Problem is that their regular is often 2-4p a litre more expensive than most of the supermarket 95Ron fuels, more so when comparing it to the unattended Asda filling stations, so can mean there's a difference of 15p a litre or more betwen the lowest and highest end of the market (discounting the really expensive rural filling stations).

Not so much if there's lots of competition in the area, e.g. the Dome Roundabout in Watford, where 95Ron at Shell is only a penny more expensive, though I suspect V-Power will be quite expensive (even if that area's fuel is quite cheap generally) when compared to the Sainsbury's and Asda filling stations' 97Ron across the road.

I tried super in my bike for a few tanks, a 600cc Yamaha designed to rev to 14000rpm. It didn't make any difference at all, and economy stayed the same at 56mpg

Most motorbikes (from Japanese and European makers) are designed to run on the fuels available in the US, which is their biggest market, and they usually don't bother adapting for other markets except in rare cases.

The 'normal' unleaded over there is 87 by the US rating method (R+M/2), which is the equivalent of 91 octane by the European RON rating. Most US stations also sell '91' which equates to our standard 95 RON fuel. So by using our 'normal fuel, you're already using a higher octane fuel than the bike is designed for :-)

My SV650's manual states to use a fuel of minimum 87 (i.e. 91 in Europe) and no more than 10% ethanol.

Just filled up in my local Texaco with superunleaded and the price differential was only 7p. The unleaded was only 1p more than the local supermarket so not bad.

Much more reasonable, as it used to be. I'll look out for what they charge locally, though there are a lot less Texaco filling stations than Shell, BP and Esso. I'm presuming they add similar additives to those from the other three.

I'm not averse to the odd tank of Super Unleaded in my SLK 350 or Mrs 72 Dudes Q3 1.4 TFSi. I don't know why because there's no discernable difference in performance or fuel economy (I keep MPG spreadsheets for all my cars since 2004)

As said previously, I work p/t hours in a Sainsburys petrol station. It can't be coincidence, but 3 of the tanker drivers who deliver our fuel from Flexigrid (which supply both supermarkets and branded fuel) always fill up at Sainsburys - no they/we don't get a discount!

I quizzed one of them last week about this. His take was that the 95 RON stuff is the same wherever you buy it regardless whether it's Shell, BP or supermarket. He did say that the likes of BP Ultimate and Shell V Power do have more additives and detergents than supermarket Superunleaded.

One thing which may be worth bearing in mind. My Sainsburys sell very little Superunleaded. We order approximately 4800 litres every ten days compared to deliveries of 15000 to 20000 litres PER DAY of U/L and Diesel. All Sainsburys fuel stations keep the tanks of Super quite low all the time. So the 97 RON you put in your car could be quite 'old'. I have no idea if it deteriorates or how fast.

Petrol does deteriorate and some of the additives used to obtain the required octane do evaporate - meaning that 97 will become 95 over time - but I've no idea how fast.

I avoid supermarkets with the constant queuing at the pumps,

Use mainly Asda and Tesco with occasional visits to Sainsburys and because they all have a large number of pumps we have never experienced any queuing issues. Both localish Morrisons have much smaller/older filling stations and there is often queuing at those.

If you really want to use a "named" brand round here you would have to go out of town and based on the prices I have observed when driving past them pay 10p a litre extra at the Shell one. The BP one seems to vary its prices throughout the day, during the rush hour its the price of diamonds, go at a time when its deserted and its virtually supermarket price.

I agree about the local variations in space. But my spacious local Morrisons seems to have every pump occupied during the day, with more customers queuing across the forcourt. .

I usually stick to the branded filling stations, without queues, albeit not at the lowest price.

And I've found somewhere to get superunleaded. No BP or Shell nearby in this corner of Derbyshire.

The town of the twisted spire nowadays. But still going to Buxton and using the A515 on occasion.

50mph is silly on the wide open bits of the A515 ,when the unclassified side roads are NSL.

But an ex-fireman told me the carnage was high. Indeed the last fatality aftermath I saw was on a 40mph section in Buxton.

With the changing 30, 40, 50, 60 and 70 and signs obscured by vegetation it can get tricky.

Edited by Glaikit Wee Scunner {P} on 17/11/2018 at 10:56