Any - Fuelish nonsense - unthrottled

Dug out some results of Which? tests on bog standard vs premium fuels (oct' 08). Here's a summary of the results:

Petrol:

Ford Focus 1.6 measured RON Wheel hp fuel economy

Esso 95 RON 95.6 81.5 33.7

Tesco 95 RON 97 82.5 34.1

Tesco 99 RON 99 82 34.5

Shell 95 RON 95.7 82 34.3

Shell 97 RON 99.6 84 34.3

Okay, lets try a turbo engine. That'll really show the benefit of extra octane, right?

VW Golf 1.4 TSI

measured RON Wheel hp fuel economy

Esso 95 RON 95.6 143.6 33.5

Tesco 95 RON 97 146.4 33.3

Tesco 99 RON 99 149.5 33.6

Shell 95 RON 95.7 144.2 33.9

Shell 97 RON 99.6 151.9 33.6

All results carried out on dynamometer either repeat runs.

Diesel:

Megane 1.5 DCI Measured Cetane number Wheel hp fuel economy

BP low sulphur 54.0 73.3 44.1

BP Ultimate 54.8 72.7 44.0

So the Super diesel performed 'worse' than the standard one (probably due to variability of the dyno).

Conclusion:

The emperor has no clothes.

Any - Fuelish nonsense - nortones2

The Which report is very scanty - in contrast with Evo issue 044 and 087 which looked at a range of engine speeds and at acceleration results in various bands. 087 looked at a GTI and an M5. The largest gain was at mid range engine speed (at 3250 rpm) torque, around 10% between race fuel and Shell 95 oct fuel. BP Ultimate at 3250 rpm was quite similar to the race fuel. This was on a GTI. On an M5 there was almost no difference. Re the M5, theory was the engine was mapped to give no more than a fixed maximum. Back to the GTI: power outputs tended to bunch together at maximum engine speeds, which tallies with richer mixture ratio beyond stoichiometric and corresponding reducton in octane requirement. About 5% overall increase for torque and power with the two best fuels compared with Shell 95. So, in conclusion, the Which report is lacking in data, but did indicate an increase in power of about 4% (atmo) and 6%.(forced) It also concealed larger gains in the mid range, which is arguably of more significance. As to fuel consumption, EVO didn't look at that SFAIK.

Any - Fuelish nonsense - unthrottled

You mean this data?

SHELL 95

Max power 205bhp @ 5600rpm
Max torque 234lb It @ 2650rpm

BP 95
Max power 204bhp @ 5600rpm
Max torque 242lb ft @ 2300-3100rpm


Shell optimax
Max power 209bhp @ 5500rpm
Max torque 242lb It @ 2500-2900rpm

Tesco 99

Max power 212bhp @ 5500rpm
Max torque 242lb ft @ 2400-3500rpm

BP Ultimate

Max power 212bhp @ 5300rpm
Max torque 252lb ft @ 2400-2500rpm

Sunoco 'Race' fuel

Max power 218bhp @ 5200rpm Max torque 248lb It @ 2500-2800rpm

The spread in torque from worst to best is about 7.5%, not 10%, and if you pick Ultimate over BP 95 the difference is only 4%.

Not trivial by any means, but if you factor in the cost difference, not really cost effective. Interestingly, they found that the supermarket fuels matched the branded fuels-which perhaps isn't that surprising given that the fuels are sourced from the major refineries.

Any - Fuelish nonsense - nortones2

Clearly you have access to the EVO reports. Surprised you bothered with the mickey-mouse Which report! Re "The spread in torque from worst to best is about 7.5%, not 10%" I was quite specific in choosing 3250 rpm, because that is where the greatest spread appears to be. What is also apparent is that there is quite a bit of variability not only between fuels (some "duff" supermarket 95 and some very good ones) but some cars reacted differently to the "premium" fuels according to the dynamometer firm. BTW, the supermarket 95 fuels were excluded because the supply was inconsistent. That didn't apply to the 99 Tesco which is from a single supplier, Greenergy. Whether higher octane is cost effective is a different issue, as there seems to be little concrete about mpg effects, and I would not trust Which on this. There is of course the detergency aspect: see Evo 044, and the amount of sulphur (sensor fouling?) is also more restricted with the premium fuels. That plus subjective results (for me) means I only use Optimax or BP, The Tesco 99 not available locally. Pity the WW2 brews are not testable: 150 octane anybody?

Edited by nortones2 on 09/09/2012 at 20:52

Any - Fuelish nonsense - unthrottled

The mickey mouse Which? report was far more comprehensive, running no fewer than 10 dyno runs to establish the average power base for each condition. They also established the actual octane rating of the as-received fuel, which EVO did not.

BTW, the supermarket 95 fuels were excluded because the supply was inconsistent.

This logic seems bizarre. It assumes that 'branded' fuels remain consistent, with only supermarket fuels showing variability due to supply. That seems highly unlikely, given that vapour prssure limits change three times/year, not to mention the different sources of crude received by refineries.

What is common to both reports is that the link between octane rating and power output is fairly weak. Neither report could demonstrate an improvement for n/a engines running on 'premium'.

No quantative report has ever shown an improvement for part throttle fuel economy.

Any - Fuelish nonsense - john farrar
Aside from the power non-difference, I would say that the premium diesel fuels produce much less smoke when I apply full throttle sfter a period of town driving. Maybe this will give me fewer problems at a later date with the EGR....I wonder.

I also have had to replace the lamda sensor on the SWMBO Mini, which I've been reliably(?) informed was down to use of std petrol with lots of town driving.I have to say that after replacing the sensor and using premium fuels everything has been fine. This could of course be down to a faulty sensor but the Mini forums seem to support the case for using premium fuels if the Mini is used for lots of short runs.

You become the victim of your experience!
Any - Fuelish nonsense - madf

I also have had to replace the lamda sensor on the SWMBO Mini, which I've been reliably(?) informed was down to use of std petrol with lots of town driving.

So your informant is saying it's unfit for prupose... Pity all the other Minis driving around town happily are not all sitting broekn down at teh roadside.

BS is my view.

Any - Fuelish nonsense - craig-pd130

In the Golf TSI, an increase of nearly 8bhp for an extra £3 or so per tank isn't bad (Shell 95 versus the high-octane brew)

It would be interesting to see the full dyno plots.

Edited by craig-pd130 on 09/09/2012 at 21:48

Any - Fuelish nonsense - thunderbird

In the Golf TSI, an increase of nearly 8bhp for an extra £3 or so per tank isn't bad (Shell 95 versus the high-octane brew)

It would be interesting to see the full dyno plots.

8 BHP at 6000 rpm is all but useless, how often do you drive at those revs. As craig-pd130 suggests a dyno plot is required to see if there are power improvements everywhere.