I'm sure this has been covered a million times
I'm puzzled my car has been mapped on v power , so that's what it generally gets
But on three occasions I've put tesco 99
The first time I thought it was my imigination , it ran very slightly lumpy
But I thought the bugs having an off day
So ran it out and topped up with v power , all smooth again
Did it again and same , still thinking its my imagination
And I've just done the same for the final time
I can without doubt confirm my car does not like tesco 99
And normal fuel is a massive no no , it hates it ( no suprise there )
Btw this is over 2/3 months so I wouldn't think it's the same batch of tesco 99
So looks like its only v power from now on


Any ideas anyone

 

im not sure if there is any difference, but im having my car remapped on 22nd and im going to use momentum and that only as its local to me and cheaper

 

I'm puzzled tbh mate , I thought they were about the same
And it's fine to use either ,
But there's no two ways , it don't Like tesco 99
Very odd I reckon

 

i only use momentum and dont swap between the two, but im sure they tested them in a magazine and there was hardly any difference.

as im getting mine mapped on tesco ill continue to use it. hopefully this will be ok.

i have had a tank or two of vpower and i didnt notice any diffrence apart from in the wallet.

 

i always use the tesco 99 as no shell on my normal route, my car hasn't been remapped.

 

You know me , top tight **** , so whatever it will run on the cheaper the better , I'm not a fuel snob or owt like that , if it would run well on p*** , I'd be drinking water like its goin out of fashion
All the 99 is from the same station , I was wondering is it summat to do with that particular station , their tanks or summat
Or is it that sensitive the ecu is noticing I'm swapping ( maybe ? )

 

no idea if is different but i thought ill get it mapped on the fuel im going to use as it makes sense.

also if tesco fuel is slightly inferior using vpower is not going to harm it

 

Don't get me wrong mate it's not running like a bag of bob on 99
But I can tell at idle , it's very slightly lumpy
If Somone filled it without telling me , I'd know summats not quite right
And if you put normal in , the car just gives in and loses the will to live

 

Unfortunately I've only got v power near me ( tesco was my back up)
If i was in your shoes I too would start looking a lot deeper and maybe look at re mapping it running on the 99 Ive been using
Was gonna do some logs and have a closer look out of interest but for what I use it's not worth it

 

I think I get more miles from tesco from the shell

 

well the map on the 22nd is just to get the car running safe due to decat and fmic and a few other tweaks.

im going to change some more stuff in the new year and get a final map so ill see how i go.

but im also planning on changing ecu too next year

 

My Type R was mapped for V power,but Tesco was nearer and cheaper so started usng that on the same map and felt no difference.

I would think though what causes the difference is HOW the Tesco 99 gets to the 99RON rating compared to V Power as I believe Greenergy may use more additives to boost octane rating (may be wrong though)

 

i tend to find tesco better than v-power during the first 2 weeks of ownership i used a different fuel each week and found tesco worked best for me, roughly same price as v-power around here! not that bothers me :P

 

Are they like for like fuels from a mapping point of view

 

I've just found an old post by Duncan dynamix

He said he found during tests 99 ran very slightly leaner

So if you're mapped on v power you may run leaner and notice
But mapped the other way round you might not

So that could answer my question

 

Depends how old, you see Tesco 99 has always been 5% Ethanol.
But over the years Vpower has also changed to 5% (ish) Ethanol.

The ethanol content by rights does affect AFR...like other octane boosting additives its a oxygenate, so more oxygen gets put through the exhaust. In closed loop mode (normal driving with warm engine) that is detected by the oxygen sensor and should cause a very slight enrichment in closed loop mode so the AFR looks normal (with slightly longer injector duration), but in open loop mode there is no AFR feedback, so things can deviate from the ideals.


I noticed this on our old Jag when Shell switched to ethanol. Its a old open loop EFi system, and whilst its a "lean-burn" engine, when the inlet air temps was high (like when sitting in a traffic jam or sat idling with a gas analyser probe stuck up its tailpipe ) it ran more lean than what I was happy with regardless of mixture trim adjustment (no mapping on this thing ), even though it actually seemed to run and perform quite happily as the octane and ignition timing was set as such to not make it detonate, in stock form its tuned to run on 98Ron anyway.

Not good for the old rubber fuel lines, but thats something I have to live with

 

maybe I can rule Duncan's test out , it was from 2007
Like I said I say , I'm not power chasing and not biased towards any fuel and if it ran on aldi 99 and it was cheaper i would use it

There is deffo something not the same in the tesco 99 I've used
The question is what

 

There is another school of thought...Could it be one fuel is bringing to light a minor problem more than the other?

For example a slightly dodgy spark plug, coil pack or plug lead could cause a cylinder(s) to partially misfire, even very slightly every now and again. Bringing up the old Jag again (sorry, its the best experience I've had on this, as lots of things go wrong on it ). One thing I noticed when switching around fuels (it was LRP vs SUL at the time) was a very slight intermittent miss on what was usually a rock steady idle. Under closer observation, a very faint spark would jump from two of the plug leads to the cylinder head. So, new plugs and leads fitted. It ran fine, for a while, then a ignition coil packed in (well, not totally, it started off as intermittent stumble and power loss, which eventually worsened to the point it packed in completely).

Coincidence? Maybe not: Typically higher octane fuel is more difficult to ignite, so stresses the ignition system more, where some spark energy can "leak" to somewhere other than spark plug electrodes causing a weak spark. Of course both Shell Vpower and Tesco Momentum are alleged to be the same RON. But we're never entirely sure what it is by the time it enters the fuel tank....the BS standard (BS7800:2006) for SUL fuels only requires them to be 97Ron (or higher).

I think there maybe a bit more to it than just the rated RON values too: All fuel these days has volatile components added to make it burn/ignite better. The problem is they evaporate, that's why cars now have unvented petrol tanks. I know for a fact if I leave my lawn mower full of fuel over winter, it'll be a pig to start next spring, it has a vented tanks. If I drain the tank and fill with fresh fuel from a sealed container, it'll start on the first pull every time. So what I'm saying is if fuel quality can affect a lawn mower engine, it sure as hell can affect a car engine. Funny thing is though, its a old lawn mower and ten years ago I never needed to mess about draining the tank. Now is it because modern fuel is not as good quality and "goes off quicker, or is because the ignition system on my lawn mower is getting old (perished plug lead and original spark plug )?

 

That sounds very plausible Ali tbh , because I only notice at idle and can't tell any difference in power , mpg , ect ( which tbh I don't think anyone can )
And that would fit in with the very slight missing , stumble , lumpy or whatever
I must stress its only very very slight but none the less it's there

 

My car doesn't like Tesco's 99.



When I say it doesn't like it, what I really mean is it doesn't pop and bang like it does with V Power.

 

My car was mapped on Tesco 99 and occasionally runs v power with no noticeable difference whatsoever

 

Im not really talking difference in power or performance mate , i would hazard a guess that if folk drove the car they wouldn't notice , it's one of those things you only notice if you really know the car

 

Had this discussion with my mapper and the general consensus was that v-power is a more stable fuel as from experience he said tesco/Bp would give more det where as v-power is a lot smoother in general, That's all I needed to know, I like my pistons how they are, He's been around the scene and mapping for 8/9 years now.

Now I'm not saying they are $hite but I have v-power local to me so it makes no difference to me, If I do ever need to out something else in I make sure it's only a bit and then top up the tank with v-power.

I have also heard that most of the higher RON fuels are the same just with different additives in them depending on who's they are, Not sure how much to read into that though,could be just hearsay but it was from a shell tanker driver?

 

As Gazza says Vpower is more stable as better quality stock fuel rather than low quality fuel that is 'boosted'. I have found very little difference between the two from an absolute power point of view but there is a difference and there occasionally is random det with tesco, possibly around 1/2 deg of timing difference between the two fuels on very non scientific tests I have done. Vpower is just very consistent and lasts longer in the tank than momentum.

Tone - that old observation of mine was when tesco were the only company using the greenergy ethanol to boost octane but they all do it now so not valid any more.

 

dunc as your mapping my car next monday would you recommend i fill it with vpower rather than tesco 99??

 

Map it on whatever your using regular or is closest to you, then the mapper will map to suit.

 

Fill it with what you usually use Dan - vpower will give best power but as said in previous posts some cars dont like swapping to momentum afterwards if mapped too close to the edge. Personally if you swap between the fuels I would map on momentum.

 

i use momentum because until last month there was no shell near me. so ill carry on using it then.
when you say shell lasts longer in the tank, what sort of time are we talking here as in the winter months my car is rarely used.

 

Could be wrong but I think it's more about smiles per gallon than actually sitting in the tank Tubbs,

 

this is true but during the winter my car isnt used much if at all.