Hitchcocks Forum

I remember an old advert from the days when I was mis-spending my youth.. "Keep going well, keep going Shell". And the Tiger in the tank..

I ran out of fuel today and had to drop into reserve mode. Luckily there was a petrol station just up the road so, no real emergency. It was a Shell station and I decided I'd give Thumper a treat and filled up with V-Power.

Now, I'm not the one to believe all the advertising crap so I didn't expect much.

BLOODY HELL! Never mind 'Goes like a Bullet'... He went like a rocket! I know what I'm using for fuel from now on...

Both My Enfields Classic Micarb,AVL Amal Carb..Like V-Power too & Sound Better on it or Extra (at other Stations)do a Couple of MPG extra too...But on Price alone the Cheaper Stuff Equals out the rise in MPG ^ Extra cost.... I remember in the Old Day's JET Petrol Made my triumph Sound great..So is it all in the mind?? (Next Post might con Firm it or Not) Nut 1 Vote for V though I do tend to run mine on anything...Cheers all.

Is Thumper still on original comp. ratio?
If so I suspect it's all in the mind.

My modern bikes, however, really do go better on "best"

I generally fill up with the local Danish produced 95 octane (although, there are those who say it's really 92).

The V juice is 99 octane. I could really feel (and hear) the difference.



Never had to tinker with the engine as such Pete, so I presume he's as he left the factory in that respect. All I did was to convert him to electronic ignition, removed that PAV crap and put a conical air filter on him. I re-jetted the carb at the same time..(about two years back..)


The only difference today was the fuel..

Bertie always gets a dose the good stuff, makes a noticeable difference to power, but with my modern Honda computer controlled everything I cannot notice the difference.

Nothing but the best for my two...

Tornado gets 97 or Vmax, whilst Kevin gets 98.

If you live in England (except South West) you could try Esso Supreme 97RON as its the ONLY petrol without bioethanol at the moment. Shell V-Power, Total, BP, Texaco etc all have EO5. Bioethanol is NOT GOOD for engines.

The combustion chamber shape in the Bullet engine is by no means the most efficient. Under certain circumstances it is liable to suffer more than many others from detonation and pre-ignition. I can well believe that a ‘better’ grade of fuel would produce improved combustion. Just how far this would be noticeable in ‘road performance’ is difficult to predict.

+1 on what Nigelphoto says. The issue today is not so much the octane rating as how much ethanol there is in the fuel. Apart from rotting various fuel system components in older bikes, the optimum air /fuel ratio for ethanol is 7:1 whereas that for petrol is around 14:1 so the more ethanol there is in a gallon of fuel the weaker the mixture will be. In the UK there is less chance of premium grade fuel having ethanol in it (up to 5% is currently allowed) than is the case for the lower grade stuff; it all depends which refinery it comes from. It will matter more when (if?) the UK adopts the 10% maximum; in that case premium will not be allowed to have more than 5%. Oh, and if you go to France be bl**dy sure not to fill up with E85 (ie 85% ethanol fuel).

Leaving the scientific explanations to Jeff or Dennis, there may be a perceived or imagined improvement in running with the higher octane fuel.

I doubt extra power and speed can be had without the addition of higher compression, knock sensors, variable valve timing and ignition timing..

However in purely practical terms, i have for years found that the old prehistoric iron barrel will run cooler and quieter with better starting and tickover when using higher octane fuel..

Regular super market fuel i have noted makes the bike sound like a blacksmiths shop, especially when increasing throttle on a incline, usually changing down to reduce pinking which i'm sure is knocking seven bells out of the piston and big end..

Higher octane = smoother running and at £20 quid a tankful i'm not too bothered..