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[Darth Loo-knee]

I always fill up at our local Tesco which has some Momentum (i think its called) fuel at 99% octane.. When my car was remapped the guy set it up using that fuel.

Over Christmas my Nanna was taken into hospital and so off I went, not even giving my fuel gauge a second thought until I was leaving the hospital grounds. So nearest Shell Station I popped into, just putting £20 in as I wanted to keep using Tesco's. Over Christmas didn't use the car much then when I did the Go..Go..Go had gone I was listening for boost leaks, looking to see if anything had come off etc etc and finally I wondered if it could be the fuel?? Never that much diiference Daz surely! so I used up the last of the £20 from Shell. Back to Tesco for the 99 stuff and YES the Go..Go..Go is back.

I was quiet shocked that it would make such a difference to the performance of the car

[Andy B]

Shell's higher octane is V power isn't it? Have you tried using that? Smart Roadster owners always go on about Roadsters being 'designed' to run on 99 Ron fuel .................. not sure it makes any difference to me 

[Darth Loo-knee]

Shell's higher octane is V power isn't it? Have you tried using that? Smart Roadster owners always go on about Roadsters being 'designed' to run on 99 Ron fuel .................. not sure it makes any difference to me 

I can't honestly say which fuel I used at the Shell Garage but could have sworn it said 97.....

if you don't notice any difference, perhaps its just that my car was set up to run on it then  just find that strange...

Anyone else notice any difference??

[Lazydocker]

I've noticed the difference between normal and V-Power/Ultimate (etc) on a bike but never in a car. That said, I've never really had high performance cars

[feeutfo]

At higher performance levels yes, on bikes.

Yours being highly tuned, doesn't suprise me there's a noticeable difference from 95 to 99 Ron.

Makes no odds in the omega when i tried it that I can tell, but then it's a bog stock state of tune.


I presume any 99 Ron will do, or is it picking out differences between supermarket 99 ron and, say, v power?
 Makes sense to use cheaper 99 Ron I guess.

[Marks DTM Calib]

I suspect he wound the boost up which in turn increases the dynamic compression ratio, that will mean it NEEDS higher octane fuel.

In fact, its not a good idea to use the lower octane fuel!

[Kevin Wood]

Makes no odds whatsoever in my Omega.

Quite noticeable in the Westfield (>11:1 compression).

As said, any high compression or forced induction engine really needs to be run on high octane fuel, especially if tuned above standard spec.

Also bear in mind that what you might be experiencing is the ECU's strategy for dealing with knock rather than purely the difference in the fuels themselves.

For example, the Omega will respond to knock with a little ignition retard, and may not be that noticeable. You might find your engine management is seeing knock and implementing a draconian boost limit. You can't reduce the compression on a natasp engine but you can reduce the boost on a forced induction engine, and this is probably the best way of dealing with knock.

[aaronjb]

There was a test some time ago in a major magazine (I think Evo?) comparing BP Ultimate, Shell Optimax and Tesco 99..

IIRC Tesco 99 had the highest power gains, though only on cars mapped to benefit of course. From memory they tested a clit, Golf and Impreza and the latter two showed gains (most from the Impreza) which really just shows they are mapped more aggressively (likely on timing) and use the knock sensor to pull back to safe levels on most fuels.. The clit clearly mapped for what it is (a shopping trolley).

So yep, I can believe it.

[Darth Loo-knee]

When Andy Forest did my re map, he had headphones attached to the engine listening for knock. He did mention that he heard no knock at all but the knock sensor was telling the ecu there was. So I am sure he said he altered what the knock sensor was hearing, but if in future I had a problem to renew the sensor.
If the fuel had made no difference thats what I would have being renewing, as the car did feel retarded......

[aaronjb]

The Mk1 Ear (and brain) is still more advanced than a piezo transducer and ECU - we can distinguish between 'block noise' and knock much more easily than a computer can

[Darth Loo-knee]

The Mk1 Ear (and brain) is still more advanced than a piezo transducer and ECU - we can distinguish between 'block noise' and knock much more easily than a computer can

But how funny do they look eh sitting there laptop on lap, headphones on, never looking up 

[Del Boy]

I notice a lot of difference when I used Tesco momentum in my 525i, it was much better on that fuel than any other 

[Darth Loo-knee]

I should get commissions from Tesco 

[aaronjb]

The Mk1 Ear (and brain) is still more advanced than a piezo transducer and ECU - we can distinguish between 'block noise' and knock much more easily than a computer can

But how funny do they look eh sitting there laptop on lap, headphones on, never looking up 

I've been that guy! First time my MR2 went out with the turbo kit on it, driven by a hooligan friend (who gave chase to an Evo!) while I sat in the passenger seat desperately trying to stay upright and map the car at the same time.

He clearly has a very different idea of "drive gently while I sort out the lower map" than me.

[feeutfo]

The Mk1 Ear (and brain) is still more advanced than a piezo transducer and ECU - we can distinguish between 'block noise' and knock much more easily than a computer can

But how funny do they look eh sitting there laptop on lap, headphones on, never looking up 

... recipe for puke on Lappy IMO.