What Fuel do you guys use?

AshCupra300

Active Member
Sep 16, 2006
381
65
Newport, South Wales
What ever is at my nearest Morrison's, I do make a trip to Tesco now and then for a full tank of Momentum, but to be honest I have not noticed any difference in MPG or Performance.
 

Maypack

Ambassador for Cumberland Sausage
Apr 20, 2014
3,175
2,327
Gods Country - West Cumbria
What ever is at my nearest Morrison's, I do make a trip to Tesco now and then for a full tank of Momentum, but to be honest I have not noticed any difference in MPG or Performance.

I started initially with BP Ultimate as that’s the nearest garage to me and when I swapped to Shell V Power I immediately noticed an increase in MPG. It actually went up about 20+miles a tank and I hadn’t changed my driving style at all.


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LouG

Active Member
Dec 1, 2017
1,319
481
Nelson, New Zealand
It would pull more timing with momentum 99 as its 99 RON over Shell's 97 or 98 (can't remember)

Octane is an inhibitor which allows the compression to be higher before the fuel detonates (pre ignition / pinking) which is bad for the engine. In order to over come detonation the timing is advanced to send the spark to ignite the fuel before it detonates..

Higher octane means that the compression can get higher and therefore the timing retarded to suit.

Octane is the measure of a fuels knock resistance usually stated as MON or RON or combined ratings. Additives such as lead in the old days, or todays toluene, ethanol etc are added to raise octane rating. Ignition timing is most definitely not advanced to minimise detonation, it is retarded. Detonation occurs when the fuel/air mixture is ignited by the spark, but part of the mixture spontaneously ignites before the flame front reaches it, hence the need to retard ign timing.
This extreme pressure/heat rise is what turns engines into grenades. Compression isn't the only factor in detonation, AFR, boost pressure, ign timing are all factors.
Pre ignition/pinking is a different thing altogether, that is the mixture being ignited by a hot spot such as carbon in the combustion chamber generally at low revs/high load. It can be damaging, but is not as critical as high speed detonation.
 

AndrewJB

Friend to SEAT UK & Cupra Racing
Aug 16, 2007
11,211
484
Maranello
Fuel can go off and loose RON over time. If possible always get it from a busy station otherwise you paying for 98 and getting lower.

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I used the one next to VW Group UK HQ as it gets a lot of use.
 

Owen83

Active Member
Feb 9, 2018
77
20
Octane is the measure of a fuels knock resistance usually stated as MON or RON or combined ratings. Additives such as lead in the old days, or todays toluene, ethanol etc are added to raise octane rating. Ignition timing is most definitely not advanced to minimise detonation, it is retarded. Detonation occurs when the fuel/air mixture is ignited by the spark, but part of the mixture spontaneously ignites before the flame front reaches it, hence the need to retard ign timing.
This extreme pressure/heat rise is what turns engines into grenades. Compression isn't the only factor in detonation, AFR, boost pressure, ign timing are all factors.
Pre ignition/pinking is a different thing altogether, that is the mixture being ignited by a hot spot such as carbon in the combustion chamber generally at low revs/high load. It can be damaging, but is not as critical as high speed detonation.

Sorry retard, not advance as you said above. I was thinking from memory, what I do on my classic car and which way I turn the Distributor depending on which fuel I put in!
 

RUM4MO

Active Member
Jun 4, 2008
7,784
983
South Scotland
Sorry retard, not advance as you said above. I was thinking from memory, what I do on my classic car and which way I turn the Distributor depending on which fuel I put in!

The trouble is, what is called retarding ends up advancing, or moving forward when the spark plug is fired, ie it gets fired earlier in the cycle which to some would be classed as "advancing" the spark, while it is being achieved by doing what is traditionally called retarding the ignition.
 

LouG

Active Member
Dec 1, 2017
1,319
481
Nelson, New Zealand
The trouble is, what is called retarding ends up advancing, or moving forward when the spark plug is fired, ie it gets fired earlier in the cycle which to some would be classed as "advancing" the spark, while it is being achieved by doing what is traditionally called retarding the ignition.

What?
Advancing spark is firing it earlier in crank rotation eg, 10 degrees before TDC instead of 5. Retarding is vicey versy. There's no confusing the issue, this is engine theory 101.
 

LouG

Active Member
Dec 1, 2017
1,319
481
Nelson, New Zealand
Sorry retard, not advance as you said above. I was thinking from memory, what I do on my classic car and which way I turn the Distributor depending on which fuel I put in!
Not to mention mapping the ignition curve with different advance springs and weights.
Those were the days. I had a selection of both and used the butt dyno and the knock sensors either side of my head.
 

Kenan

Active Member
Dec 14, 2018
194
73
if this is the case then V Power is pointless as my guess is that a LOT of people wont pay for it
Think it only happens after months in the tank for degradation to happen.

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Maypack

Ambassador for Cumberland Sausage
Apr 20, 2014
3,175
2,327
Gods Country - West Cumbria
if this is the case then V Power is pointless as my guess is that a LOT of people wont pay for it

That’s why it pays to go to a garage where the V Power Pump is in use a lot. My local Shell garage is approx 8 miles from me and is the only V Power in a 30 mile radius and it gets used a lot due to the number of Cupra’s, S3’s, R’s and other marques models that require it being in this area.


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Kenan

Active Member
Dec 14, 2018
194
73
So just went to my local petrol stations for a price check (not had the Leon long).

Shell V Power 99RON £1.39
Tesco Momentum 99RON £1.33

So I'll be used the Tesco then thanks. Didn't think the price would be that much.

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GordonMcC

Active Member
Feb 8, 2017
284
153
31
Ayrshire, Scotland
So just went to my local petrol stations for a price check (not had the Leon long).

Shell V Power 99RON £1.39
Tesco Momentum 99RON £1.33

So I'll be used the Tesco then thanks. Didn't think the price would be that much.

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Where i am Tesco 99 is £1.28
Shell V Power is £1.41
 

Maypack

Ambassador for Cumberland Sausage
Apr 20, 2014
3,175
2,327
Gods Country - West Cumbria
Where i am Tesco 99 is £1.28
Shell V Power is £1.41

No idea how much Tesco Momentum is as the garage is over 25 miles away so haven’t been near.

V Power near me is £1.35 but with the usually 4-8p off vouchers I’ve been getting using the Shell App, I’ve been partying around £1.27 - £1.31. And compared to BP 95 RON being £1.28, I didn’t think it was that bad a price.


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GordonMcC

Active Member
Feb 8, 2017
284
153
31
Ayrshire, Scotland
No idea how much Tesco Momentum is as the garage is over 25 miles away so haven’t been near.

V Power near me is £1.35 but with the usually 4-8p off vouchers I’ve been getting using the Shell App, I’ve been partying around £1.27 - £1.31. And compared to BP 95 RON being £1.28, I didn’t think it was that bad a price.


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no at £1.27 I dont blame you but what do you have to do to get those kinds of discounts?
 

Maypack

Ambassador for Cumberland Sausage
Apr 20, 2014
3,175
2,327
Gods Country - West Cumbria
no at £1.27 I dont blame you but what do you have to do to get those kinds of discounts?

I guess I’ve just been lucky and I use the Shell App on my iPhone and they just keep popping up. Sometimes in the form of a £X points off or 8p off per litre.

Don’t know what I’ve done to earn them but they help.


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