The only answer is a double blind test using a large number of owners of the same model of car!

also need to take into account tuning, driver driving style, type of driving etc.

i had the exact opposite of you sms, i run mine on tesco 99 and i had to put either optimax or vpower in it as there wasn't a tesco nearby and it ran like crap.

mine runs perfectly on tesco fuel

Evo magazine did this some time ago. I think the winner was Tesco finest.

Audi mag did a comparison a year or so ago and found T99 overall the best, plus was more stable when stored for 1wk or more compared to BP and Shell.

The other thing I've noticed is that the car is much smoother when engine is cold. [This is 99 compared to 95]. On 95 there was a lot of hiccups at lower revs till engine was hot, now this is almost unnoticeable.

I think it is all pychosomatic personally, no one can tell the difference that accurately,

If I told myself the car had rocket fuel in it I would think wow and drive accordingly, if i said to myself it had dog poo in I would notice the smell and wonder why the car is slow.

It is all in your heads people if you think a car benefits from a slightly higher octane fuel!

I wouldnt mind if we were running around a racetrack in 600bhp monsters...

I think it is all pychosomatic personally, no one can tell the difference that accurately,

If I told myself the car had rocket fuel in it I would think wow and drive accordingly, if i said to myself it had dog poo in I would notice the smell and wonder why the car is slow.

It is all in your heads people if you think a car benefits from a slightly higher octane fuel!

...

That's why double blind tests are so important. (More in medicine, I agree) but it is the only way of getting rid of the human factor, placebo effect, and all that!

You'd fill up a lot of cars (of the same model), not telling the driver, or the person doing the filling, what fuel was going in. Ideally do several tanksful, get their reports after each refill, and see who says what.

Results go back to the experimenters, who are the only ones who know who had what and when. Then see if you get a statistically meaningful result or if the drivers' beliefs were totally random, and unrelated to what they had in their tanks. Shouldn't take more than a couple of years!!!!!!

Mine seems more than happy with frescos finest.

V-power is V-expensive in cardiff as there is only one shell station so I don't ever bother trying it. I did buy some a few weeks back in Swansea and couldn't tell the difference tbh.

A lot of the time it is just that placebo effect. The only time i used tescos 99 was in summer. It was hot and felt gutless. Could be cos car has only ever been run on vpower and it needed to run a few tank fulls to adjust to it. But when i next filled up with vpower i did about 25 miles and the car seemed like normal again.

V-Power (99RON) is 96.9p/litre in Huddersfield, and in Okehampton! Seems a bargain to me.

On another note, Shell V-Power is 100RON in Germany and Austria! What's that about? My car bloody loved the stuff, and I was seeing decent mpg gains on it too.

I use Shell because I have a Shell card, and they gave me loads of toy cars!

V-Power (99RON) is 96.9p/litre in Huddersfield, and in Okehampton! Seems a bargain to me.

!

Last time I looked at the one station in cardiff it was still about 15ppl more than tescos :eek::eek:

for me it's down to miles per tank.

Managed 300 today on v-power before the fuel warning light came on.

Filled with optimax to see what I get from that.

Next it'll be v-power

for me it's down to miles per tank.

Managed 300 today on v-power before the fuel warning light came on.

Filled with optimax to see what I get from that.

Next it'll be v-power

you need to run it right down to near nothing and fill up to top with same fuel 3 times and take the third fill up reading, the ecu needs to adjust to each tank and this can take up to several hundred miles so then once its got to that point it will only be from then that you will get an accurate account of what that paticular fuel brand is actually like.

Swapping to different brands after each fill up isnt accurate.

you need to run it right down to near nothing and fill up to top with same fuel 3 times and take the third fill up reading, the ecu needs to adjust to each tank and this can take up to several hundred miles so then once its got to that point it will only be from then that you will get an accurate account of what that paticular fuel brand is actually like.

Swapping to different brands after each fill up isnt accurate.

I have a 1.8Tsi - Do these things really adjust slowly to the fuel octane - what do they adjust from - the Lambda sensor is looking for oxygen (fuel mixture closed loop) Is there a pre-ignition (knock) sensor. I assumed higher octane fuel just burnt slower allowing for more controlled burn & higher compression ratios or is it's calorific value higher - (like diesel giving more mpg) Any one know ?

i think its a number of things after my last service it took about 150 miles for the car to learn my style again. you also got to remember that each fuel needs to be diluted out of the system when trying different fuels to get the optimuim performance from it etc.

I have a 1.8Tsi - Do these things really adjust slowly to the fuel octane - what do they adjust from - the Lambda sensor is looking for oxygen (fuel mixture closed loop) Is there a pre-ignition (knock) sensor. I assumed higher octane fuel just burnt slower allowing for more controlled burn & higher compression ratios or is it's calorific value higher - (like diesel giving more mpg) Any one know ?

Mine is a 1.8TSi now too and I thought it wouldn't matter if I ran it on 95. It is very different on 99 and I'm only half way through the second tank.

It is nowhere near run in yet so I don't know if the difference is partly that, but it is not a question of more power - I can't judge that as I don't drive flat out.

But it is more responsive, smoother and certainly from start to 'warmed up' it is much happier on 99. That might apply to any other "super" too, but as Tess 99 is easily available and cheap (-ish !!!) here, I might as well use it.

People might be intrested to know that from Jan 2009 all UK fuels have to become less than 10ppm sulphur:

Sulphur -free petrol and diesel

From what I understand from all reading up on this the FSI/TFSI VAG engines are designed to run on sulphur free fuel, according to 'Honest John' it's not VAG engines that are at fault but UK's 95 RON petrol and it's high sulphur content vs what's on sale in Europe. And the only way around this is to buy Optimax/98Ron/Tesco 99 etc now which have less than 10ppm sulphur.

But in January all UK fuels become less than 10ppm sulphur and the benefit of 98 RON+ becomes less needed.... Thoughts any one?

James.

that is interesting, id be interested in what others come up with from going to 95 from 98.

You'd fill up a lot of cars (of the same model), not telling the driver, or the person doing the filling, what fuel was going in. Ideally do several tanksful, get their reports after each refill, and see who says what.

Results go back to the experimenters, who are the only ones who know who had what and when. Then see if you get a statistically meaningful result or if the drivers' beliefs were totally random, and unrelated to what they had in their tanks. Shouldn't take more than a couple of years!!!!!!

Hey, if you are paying for what goes in the tank I'd like to volunteer both my vehicles for this trial, and if it takes 5 years or more to get meaningful results, that is OK by me too

that is interesting, id be interested in what others come up with from going to 95 from 98.

Well I last week put a tank full of 98 ron in my car after reading this site and others site, never really bothered in past with last cars. The best avg MPG (via trip) in my new Skoda was 36.7mpg but best since this 98 RON was today at 44.8MPG! On the same roads and style of driving etc. So 98 RON is a winner for me, only downer is the £1.19 a litre cost:eek: from my local one and only petrol station that sales 98 RON.

James.

have you tried to find a shell garage and used vpower instead as thats now around 95.9p a litre

trust me they don't have it up here...

the tesco here in Haverfordwest (west wales) dunt do the99 only 97. i use it in my mk1 as the 97 gives better MPG but the 99 i use in bristol is better power.

mind the tesco in brighouse up home only sell 95. last time i was up

have you tried to find a shell garage and used vpower instead as thats now around 95.9p a litre

Love too but I live on the Isle of Wight... one and only place that sales 98 RON: Tesco's and all the rest just 95 RON from 88.9p per litre. I think 98 petrol station knows they have the monopoly locally and can change what they like... Seems good stuff however just going to cost me £7 more to fill up!

James.

We shop at Tesco (Holmbush, Shoreham) and with my 5p litre discount I paid 89.9 per litre for 99 on Friday last!

It was like waking up in 2004 or somewhen.