scoobyman223

iTrader: (7)

Morning all
Just after some people's thought's my car is remappped running in the mid 350's and normally i run on tesco 99 fuel. i got caught short in London the other weekend and filled up with sainsbury's super although alot of journey was on M1 my car seemed to run no different.. over next few days performance got worse to the point you could feel she wasnt as urgent on overtakes etc so ran fuel almost empty then filled her back up with tesco 99 at start of this week..now i know there's alot of hype over so called super fuels from supermarket's but now she's back on tesco 99 my car is back to rude health i did no batt /ecu reset just left her alone my question is have fuels really moved on that well as from my perspective tesco 99 seems to be the best over shell, sainsbury's super etc any thoughts.. i found this info and it seems to mirror what my car is telling me by feel,smoothness and just general ooomph

Momentum : 99 RON
V-Power : 99 RON
BP Ultimate : 97 RON
Waitrose Super : 98 RON
Sainsbury's Super : 97 RON
Texaco Super : 97 RON
Esso Super : 97 RON

kev

LuckyWelshchap

I might as well start the 'discussion' then.

Firstly, I feel that Momentum is the best choice for mine. Definitely more economical (by about 5-even 10% over V-Power) and feels sharper, especially pulling in lower (2-3K) rev range.

Next, as I understand it the ECU, although programmed (mapped) for optimum performance on the optimum choice of fuel ie. 99 RON is intelligent enough to detect less than optimum running - caused for example by less effective combustion due to lower-grade fuel - and compensates by retarding the timing. This prevents the fuel combusting too early ('pre-det' or 'det') and hence the engine continues to run smoothly, though producing reduced power output.

When you filled up there would have been a mixture of fuels, so the actual RON in the tank would (put very simplistically) have been somewhere between 97 and 99 (although far closer to 97).
Motorway driving doesn't place substantial (even significant) demand on an engine, especially one such as yours and so you wouldn't have noticed the drop in performance that much.

However, a return to more demanding driving and you'd certainly see the difference.

When you refilled with 99 the ECU simply didn't have to take the corrective action and hence the engine/car returned to 'normal mode'.

scoobyman223

iTrader: (7)

Thankyou
Seems the Larger petrol companies could learn a thing or two about making good fuel although they all probably go through the same refinery i think Tesco's Tech people have the final mix spot on ..

Fantastic detailed reply though so thankyou

LuckyWelshchap

Thanks.

I couldn't believe I was about to chuck Tesco stuff in the car, but as always plenty of advice from people here to give me confidence.

I'm concerned about the lack of responses.
Either I'm starting to get geeky and no-one can point out any error or the plague has wiped everyone out.

scoobyman223

iTrader: (7)

There all rushing out to Tesco's lol

madscoob

iTrader: (3)

the way i understand it is this.
the lower the octane rating the earlier it explodes, therefore with a higher octane rating the later it explodes allowing more ignition advancce allowing more performane. remember old cars where you could tweek the distributer cap to the point where it would be a bitch to start but go better, that kind of explains it but the ecu does it for the car

thenewgalaxy

You can run an STi on a lower fuel grade if it is mapped for it (though some don't recommend that) but you can run one of these engines on 97 IF you run the engine off boost.

I try to brim mine when I fill up with the Tesco stuff as it feels like the best one to me. Not much in it but the car just feels better slightly. However V Power is the more common fuel round here and I invariably use that more.

V Power is the only alternative unless you count that mad BP 102 stuff in London, Manchester and Birmingham at selected garages. Think it's around 2.50 a litre. Never put it in any of my cars so can't really comment on anything other than the price!

Djgyro

And I thought it was just me being paranoid!

I religiously run on V-power because the previous owner said I should and figured it's a good fuel so never questioned it (plus get to collect Avios
In my neck of the woods a lot of Shell garages are being taken over by Apple fuels so I occasionally have to resort to Momentum. I noticed if I'm gunning it my Scoob hesitates on power application on Momentum but there's a definite 5-10% fuel economy gain.

Stranger things have happened.

alcazar

iTrader: (2)

Some of us have run exclusively on Tesco Momentum for years.

However...that COULD have something to do with the fact that we used to have two Shell garages here, but the utter b@st@rds closed both within six months, so the nearest Shell is now over 30 miles away!

LuckyWelshchap

Oh-oh, everyone's agreed with me.

Friday 13th tomorrow is going to be a b!tch, I just know it........