dodgy bp Ultimate?

[pjac67]

Normally fill up with Shell Optimax. However...drove for 250 miles yesterday (top down of course) - no problems other than when topped up tank after c. 80 miles(20 litres) with bp ultimate. Car sounded awful on start up, and cut out. I checked that it was unleaded and not DEISEL! - phew!, started again, coughs and splutters gave it some revs to help along, went 10 yds, cuts out. Started again, kept revs high after initial protest - no susequent problems (had a full tank of bp ultimate on the way home). Any thoughts? Thanks, Paul.

[blujay10]

Hello mate!
Check the Chim Thread "engine cutting out" sounds similar (?), but hopefully it will be better when you re fill with Optimax..I had a similar problem when i used 5 litres of ASDA 97 RON to get me home - never again!

[bigdods]

There have been lots of posts on this kind of thing on the Chim forum - IIRC its down to the ECU having to relearn due to the different octane rating of the fuel. Shell is 98, BP is 97 - I run BP in my 450 but had to fill up with Optimax once and it drove like a b'stard , lumpy, nearly stalling, revs all over the shop on idle. I think those who know more than me said it takes the ECU a full tank to relearn....

[McBob]

Theres an article in this months EVO where they tested various fuels: from 95 RON up to turbo nutter race fuel (using a Golf and a BMW M5). Made pretty dull reading, but the conclusion (and I'm para-phrasing greatly) was that there was about 10% variation in total BHP from best to worst. From memory I think that the order (best first) was

TN race fuel - fantastic at high revs
BP ultimate - as good as the TNRF at lower revs
Tesco 99
Shell Optimax - lagging behind the first three a little
branded 95
supermarket 95.

The most interesting point in the article was that there was great variation in performance from what ought to have been the same fuel - depending on whether the forecourt was busy!! Apparently the fuel goes off in the storage tanks! So the moral of the story is to stick with the one fuel (so your ECU can adjust to it) and buy from a busy forcourt just as the tanker pulls away.

[havoc]

McBob,

The article also said:-

- Different cars respond best to different fuels, find what works for your car
- Optimax was the one that "felt" the best to the driver - better top-end and cleaner sound, apparently.

[pjac67]

Thanks for all the replies - will be reading my copy of EVO tonight! I new there were variatons on performance/MPG but I guess the ECU getting used to the new stuff caused the cut out - never knew it would make that much difference ( especially on only topping up from 1/2 full!). Optimax rules!

[jeffsy]

IIRC correctly Im sure I read somewhere that fuel should settle in the tanks at petrol stations so perhaps its best not to go straight away after a delivery

Beware, I may be talking absolute bollo , but Im sure someone who knows what they are on about mentioned it

Oh btw...I had similar problems to the ones you mention in terms of spluttering. holding revs etc after filling up. I got the stepper motor cleaned out and (touch wood) no further problems - and we use several different garages

[pjac67]

Thanks Jeffsy - time from fill up to setting off was c. 10 mins BTW. Car sounds much better today (new sports exhaust fitted yesterday!).

[kevinday]

jeffsy said:

IIRC correctly Im sure I read somewhere that fuel should settle in the tanks at petrol stations so perhaps its best not to go straight away after a delivery

Yes, because there is always some undesirable stuff such as water in the fuel storage tanks, so letting it settle so the pump does not pull it through is a good idea.