I have bough Optimax/V-power for some 15+ years. Smoother running, quieter & seemed to be marginally nippier.

The premium was modest -say 6p +/- for most of the time.

Of late however it seems to have grown to 15/16p per litre, in my area at least -Shell & Esso.

Last 2 x 50 litr fillups have been Jet 95 octane.

Personally, I think the fuel companies/filling stations are just trying it on, especially because there's so much negative press about the (supposed) consequences of using standard diesel combined with regular short trips from cold. Unlike with superunleaded (and especially the branded ones with more detergents in them), 'super' diesel does not raise performance by virtue of having a higher cetane rating - they don't - they just have more detergents to keep the fuel and combustion/exhaust system clean.

Whether this is more cost effective than buying reputable fuel additives is another matter - with the current large disparity in prices for both super unleaded and super diesel from their 'regular' varieties, I'm inclined to think that anyone who doesn't have a moderate (e.g. over 150hp) to high performance car that can gain a decent performance boost (petrol engines only) are wasting their money if they do sufficient mileages per trip at reasonable speeds above 40/50 mph.

I found that if you get such cleaners on offer, they offer a very similar (at least) cleaning effect at a quarter of the cost of super unleaded, but then I have a 12yo petrol engined car which isn't DI and obviously doesn't have a particle filter. Whether having one (all newly designed cars are now supposed to have them, petrol as well as diesel) makes a difference, I'm not sure.

The premium was modest -say 6p +/- for most of the time.

Of late however it seems to have grown to 15/16p per litre, in my area at least -Shell & Esso.

It's about 12p per litre extra for super petrol / diesel here (Macclesfield), but in Wales last week, Shell's regular 95 octane brew was £1.289 and the V-Power was £1.499: 21p extra per litre.

I suppose the filling station might argue that they don't sell very much of their superfuels, so they price it accordingly; I'd argue that they certainly won't sell very much of it at that price/

I have been running mostly diesels since 1959 (Vauxhall Velox with a Perkins 4/99 engine). For the last 40 years I have been running almost exclusively diesels and have clocked up well over half a million miles in them and have honestly not noticed any difference in the fuel I have used.

I have been using supermarket fuel ever since it was introduced, primaraly because its cheaper, never had a problem with it or detected any noticeable difference in consumption or running.

This forum is slightly different to others, because most of us take an interest in our vehicles, they are usually bought after careful thought and research or prior knowledge as best we can, many of us are mechanically minded and do much of our own maintenance, others don't get their hands dirty (cos well heeled :-) ) but can tell whats going on and seek to maintain their vehicles for a long life, some even servicing their vehicles correctly over and above the miniumum suggested in some comical handbooks.

HJ caters in his colums for all sorts of motorists, many of whom are utterly clueless whats going on, whether they have a DPF DMF or any other three letter acronyms fitted, let alone have any idea whether the car is running right, basically they are white goods car users.

Whilst we tend to do what we hope is best for our vehicles, often tried and tested methods over many years, the white goods owners maybe need a simple solution that might just help them to run their cars without too much trouble, so if HJ's suggestion of Shell or whatever Super Diesel helps reduce regens and EGR troubles down the line that the white good owners haven't even a clue about, then that can only be a good thing.

For what its worth, i tried Super Diesel in the Landcruiser for a few months, never noticed any real difference to the supermarket stuff, so i've resumed same as above, i dose the tank with Millers and a good measure of 2T oil before every supermarket fill up, so far so good, not recommending others to do the same, what suits my car my use may be quite different to others.

Also, us regulars here on this forum generally look after our vehicles and treat them with a bit of mechanical sympathy eg few here would switch a hot hard worked turbocharged engine straight off nor expect to thrash it from cold, have you noticed we don't tend to suffer (hope that doesn't rebound expensively) the ills that so many others do with their cars, not so long ago we had a MINI owner who wondered about high oil consumption when he'd several times only checked and topped the oil up when the low pressure warning light came on, most replies here were sympathetic to the car, you cannot help some people.

Edited by gordonbennet on 24/06/2018 at 10:04

Unlike most, I can and have proved that my Saab B207R makes 16hp and 26Nm more on Tesco M99 than on standard BP unleaded.

If the car is factory mapped to produce its max power on 98/99 RON it will do that on eitherTesco Ultimate or expensive Shell (whatever they call it). Run it on 95 RON and whilst it will be safe (providing the knock sensor is working) it will produce less power.

The VAG 1.4 TSi is specified with 95 RON but it says in the fuel flap that the use of 98 RON is OK as is 91? RON (which ypu cannot buy in the UK). Look in the handbook and it goes on to say that with 91 RON it will produce less power but using 98 RON will be of no advantage.

Take my Caterham as another example, when I fitted fuel injection I had a choice of map, one using 95 RON and one using 98 RON. Since its not a turbo the difference would be small (by the mappers own admission) but even though every little helps power wise it seemed daft to me to be stuck using 95 RON if there was no 98 RON available especially considering there was no provision for a knock sensor with my set up.