John Rumm wrote:
dennis@home wrote:

That is unlikely.
There is virtually no difference between them and they frequently come
from the same tank.


I can't recall which mag did the work, but recently saw a quite detailed
analysis following a batch of tests of different fuels. They compared
supermarket petrol, against branded and also (IIRC) Shell optimax. They
used three test vehicles; a Nissan Micra, a VW Golf GTI, and a Subaru
Imprezza WRX. The test was well done using a dynomometer to assess power
and torque delivery, and the tanks were correctly cleaned and the EMUs
reset between tests.

The results were interesting - the main upshot however was that on the
Micra the different (and more expensive) petrols made very little if any
difference to either the performance or the drivability of the car. On
the Golf there was some improvement in performance on the optimax (about
8 - 10 bhp IIRC) and a slight improvement in driveability. However on
the Imprezza there was a quite substantial improvement in power (over 25
bhp) and driveability.


The survey was on Fifth Gear, Channel 5 a couple of months ago. I
probably have a recording somewhere.

john2