abbott

105.9 p a litre i just brimmed my tank on my way to work and it nailed me to the tune of 43.00 i cant complain as i knew when i bought it it was gonna cost me a few sheckles to run ! i filled up in edinburgh last week and it was only 99.9 a litre its brutal to think just coz i live in inverbloodyness i have to pay extra !!

Northern Nick

iTrader: (1)

You have to pay for the beautifull views one way or another

cos500

I use sainsburys super and the car has run on that for years with no problems.

andyseston

pay 101.9 for my v power and i also use a octane boost in it to get it to the 100 octane mark and makes a great diffence and i will only use v-power

Going 4 400bhp

iTrader: (2)

I notice under everything you write it say's you need more money to sort out your car? Maybe paying too much for fuel

Iv just booked my car in with jollygreenmonster and im getting it mapped on 97ron... V power my ***!

midas303

A mapper will map your car with whatever fuel you turn up with..

Mines mapped with V power and an addative....Not the smoothest running Scooby and not as smooth as it was at 303bhp.

Now this is most strange...I try to use V power all the time and where I live there is one local and another on the way to the M6. So 99% of the time it gets what it was mapped on..

When I can't get V power I use BP Ultimate..........and guess what....It runs really well and smooth but maybe not quite as quick....don't know.?

Is it me?

RBGUS

iTrader: (7)

I use the v power cause thats what andy f maps the car for.The price for this fuel dont really matter,worth every penny imo

Northern Nick

iTrader: (1)

So your not wanting the best out of your car, you just want it to run right on 97ron, theres nothing wrong with that. Why not just get it mapped on 95ron and save yourself a few more pence when you fill up.

But your claim regarding saying V-Power is no better than any other fuel has no grounds.

If your happy with 97ron, fine.

Shark Man

Could be the 97ron has a higher calorific value than the V-power due to it being diluted with all the various additives.


Whoosh!

<btw that was the sound of post #12 flying over everyones head >

Northern Nick

iTrader: (1)

I read it

Northern Nick

iTrader: (1)

Just thought this might interest while we're on the subject.

Tests done on an Impreza also.

Fuel Tests

Spyd

Hope that wasn't aimed at me, if i was gonna moan about fuel prices and economy i'd refuse to use the most expensive.

Can't deny that everyone would be happier with lower prices on anything not just fuel.

Steve Whitehorn

iTrader: (13)

Big thread on here a few years back about this.
People that really knew there stuff got involved
will see if I can find it - but it was a while ago now.


As Shark Man says - Higher octain is just about not making it det sooner.
The quality of the base fuel is key. The additives just add octain points as it were. all high octain fuels are are 95-97 whatever with a load of additives -often ethonal to take them up to 99-100.
Mapping v the fuel is the key really.

I will see what I can turn up
Steve

dave_usuallyonpistonheads

So if you get your car mapped using 95RON what happens if you then but Vpower, T99 in the tank.

Do you go faster? Or does is chuck it's dummy out?

Shark Man

Probably won't feel a thing, might even lose a few horses if the the ECU can't advance the ignition enough to compensate for the slower flame front.

XR-Wayne

I was Mapped on V Power, If i was to Use Esso, or Sainburys would i be making a mistake. Only really used as a fast road car. Some times cant find a Shell and always think should i risk putting a Super from Sainsburys or Esso in. BP is proper crap. Did not run right on my car. 2003 WRX

Phildodd06

I would of thought as long as the ron is the same thn you wouldnt have a problem

XR-Wayne

Esso and Sainburys are 97 RON aint they?

Shark Man

It should be ok, if the car has been mapped well, it will have some safety margin, and if it does detect knock, being a newage it should compensate. If in doubt - ask the person who mapped it.

But obviously it will run at its best on the fuel it was running on when it was mapped (presuming its a tailored map)- even though different brands have the same octane; the additives used can differ; and can affects how the fuel burns. So some will work with that map better than others. We're not talking huge differences here, but maybe enough to notice slightly in extreme circumtances.

If one does notice a problem, be it pinking, slight loss of power or driveability. Drive gently and take it it easy on that tank and refill with something else or your normal fuel and chalk it as a lesson learnt.

Also bear in mind how often a particular forecourt sells their super unleaded fuel (in comparison to super unleaded), Super unleaded fuels being more likely to be left stagnating in the forecourt's tank gathering condensation, losing octane, through the fact that less people buy the stuff.

simscooby

Interesting thread guys. I'm really glad I read through it all. I've had german cars for the past 3/4 years and used to use V-Power. I then changed to Ultimate about a year ago in my current E46 3 series and have never looked back. Found the car to be more responsive and smoother.

Had I not read this I would have been filling up my new scooby on Ultimate as soon as I picked it up. I think I'm gona make the decision to go back to V-Power as I have allways been happy with it and it sounds like the general feeling is it is much better for the scoobs than Ultimate.

blu scoob

tesco is the cheapest and 99 rom sainsburys isnt super,they say it is but it sent the wifes fsti into limp mode,I took it to RC for a remap and the brain wouldnt let it map until they put super in v power is to dear

Lateral Performance

iTrader: (20)

Why does an oxygenated fuel need to run "richer" ? Wouldn't the AFR remain the same.

Also, higher octane fuels can be run "leaner", so wouldn't this give better fuel economy, comparing "like for like" driving ?


Mark.

Paul3446

I'm paying 86.9 for my petrol at Tesco at the moment!

Shark Man

Sorry, I over-generalised too much there as there two issues here: If the fuel has a high level of oxygenates, the ideal AFR is still similar for thermal efficiency, but more power can be achieved if the fuel is run richer (why that is I'm yet to exactly work out, but its partly down to calorific values), however the other complication is the way AFR is measured causes issues: "Oxygenated" should leave a clue there, the issue in which more residual oxygen will pass out the exhaust after combustion and be detected by the oxygen sensor; which if using a factory map will detect a lean running condition and thus make the car run richer to compensate. Ok for power (as oxygenated fuels can give more power if run richer), but not so ok for optimum AFR that fuel could be burnt at (economy).

Complications arise depending on the car; an old narrow-band equipped car won't be fussed at full throttle as it ignores the sensor, but at part throttle cruising its going to end up running richer than needed. So its opposite to the ideal. Wideband cars are affected too but will benefit from the enrichment on full throttle, plus they are easier to tune to compensate and take advantage of the fuel used.

Obviously the amount of oxygenated additives used is the real issue here, which is why nobody can dump in e85 bio fuel without doing some serious remapping.

Phew

In an over generalised answer; Yes. However the reason why is not totally down to the fuel's octane rating.....

Factors remain with what is used to make a particular fuel higher octane (tip of the iceburg mentioned above), which will make some high octane fuel better than others: For example its reported that Toluene is a superior method of boosting octane than using ethanol or or other oxygenates - it gives higher octane, but doesn't reduce the calorific content.

It is plausible to think that one could get a 95Ron fuel that has a higher calorific value than an higher octane oxygenated fuel, so on paper more economy could be extracted from the lower octane fuel. However if the engine can't run at its ideal AFR and ignition timing, then the reality will differ....

Which is why one has to consider the reasons to a particular car's inability to run on low octane fuel without over-retarding the ignition timing from the ideal and dumping in more fuel to quell detonation.

Maybe I should mention that ignition timing advance is almost always going to be lower with a lower octane fuel as these generally burn faster; that in itself is not the problem, it just has a different ideal ignition point. The problem arises is if it burns uncontrollably or auto ignites requiring ignition to be retarded from the ideal setting and mixture enrichment.

If the engine due to its physical design (crap combustion chamber design, poor thermal control, excessive compression, too much boost etc) cannot run happily on a lower octane fuel, then yes, it will lose power and return poorer mpg because of that. Relating that to an Impreza Turbo; off boost with a 8.5:1 compression ratio it would run happily on anything and be more economic on a fuel with a higher calorific content...BUT add boost, thus compression and heat and it'll quickly spit out its dummy.

Well that little lot padded out my last few minutes before lunch. TTFN!

[Davey]

I think some Impreza owners a little bit cuckoo when it comes to petrol and MAF's lol..

Octane ratings are unstable anyway.. Personally I use standard SUL and cant tell the difference between SUL at my local Total or the 'special' fuels at my local BP or Shell other than the price. I think some people just feel better paying more money for something, its like its some confirmation of quality? who knows!

exvaux

iTrader: (1)

my problem isnt cost theres just no shell garage for miles,i use tesco with millers OB as the car didnt like bp ultimate

RB5_245

Diesels manage to run quite economically despite it's slow flame front

If you can reach MBT at cruise with 95ron (I have to assume you can, and do) then you can run leaner with a higher octane fuel.

Additives and theories aside a modern ecu can deal with this and you can see the results. It just won't make a blind bit of difference if you drive a renault 4

Also, I have heard from good authority that V-Power is a higher quality base stock fuel than the likes of tesco. Don't ask for the figures though, no idea when I read this.

Dave