Z4 on different fuels

I have never foound V-Power to be worth using, as compared to our local (in France) supermarket 97 octane petrol it never lives up to its promise - cruising at 80 mph on a level autoroute I usually get about 35 mpg, but after refilling with V-Power consumption rose to 28 mpg - hardly the sign of a wonder fuel!

In the UK, I gave found the same effect when using V-Power, and would not reccommend it to anyone.  Lots of enthusiasts claim that their car feels as if it is going better, but when you press them it is really just a feeling - a seat of the pants or wishful thinking judgement.

I have found the same thing when using the BP equivalent, and would bet that both fuels obtain their 100 octane + rating by means of a methanol overdose - giving knock resistance at the expense of performance.

I found the very best UK fuel was Esso Supreme 97 octane, and their 95 octane a close second, either giving better fuel consumption in the same driving style than any of the UK other fuels - irrespective of their claimed octane rating.  Not having used the Z3 in the UK for about three years, no doubt the quality of your petrol is now worse.

Any increase in the fuel's knock resistance will enhance performance slightly, due tothe ECU advancing the ignition timing a little, but the real alswer is a fuel made from a better crude stock, and/or with less ethanol adulteration.

Remember that octane rating is not a sign od the fuel's power-producing potential - just its anti-knock rating.  Current UK petrol has at least 5% ethanol, and may contain a greater percentage - ethanol is a cheap way to prevent pinking, but like all other alcohols it is a poor fuel.

On the subject of fuel system cleanersI have used Millers Power Plus and it s predecessors for about thirty years, and found that it kept the injectors of our Golf GTI spotlessly clean, making my usual practive of removing them for cleaning every 50,000 miles to ne unneccessary.  The effect must be similar to having the injectors ultrasonically cleaned, but the effects are maintained, rather than gradually reducing.  It is also a mild octane booster, and due to maintaining the spray pattern of the injectors also acts as a combustion optimiser.

I have always used their diesel additive in our Golf TDI, which after 216,000 miles have never needed its injectors removing - draw your own conclusions . ..


Edited by Mike Fishwick - 31 Jul 2016 at 2:03pm