Shell Optimax/Nitro Plus, C5 V6.

[Quackers]

Anybody had any experience with this fuel?

Popped a full tank of this in the V6 C5 (2001), and the car has been getting progressively worse power wise since, to the point now where its struggling to climb hills. In normally driving its really struggling to get past 3000 revs and sounds very roughy and made the engine management come on (although that does not take a lot on a first gen C5 ) Its only since the last tank of fuel this has started.

Is its just coincidence or is this fuel really bad for some engines? I was speaking to one friend and he said he started using that stuff just before his cylinder head went in his MG. Hoping somebody else has tried this fuel and it aint agreed with their engine and simply putting normal unleaded in makes it go away

[addo]

Are you 100% certain there's no physical cause? Restricted fuel supply or exhaust blockage?

[bxzx16v]

I've never had any issues in my Zx16v with the Shell fuel , as Addo says could it possibly be something else causing the problem ?

Mark

[SaabC5]

I think its just coincidence. I don't think a higher octane premium fuel will make a car run worse than using standard unleaded. Most modern cars can adjust the mixture ratio according to the RON rating of fuel used due to varying quality of fuel available worldwide.

[isisalar]

I've been using shell v power diesel in my Xantia HDI for about 6 months now and the cleaning properties seem to have improved the performance with every fill. Used the wife's old 106 diesel for a while and after filling with the V power, over a few hundred miles I could feel things cleaning out and it would run a little roughly, then it cleared and then ran better than ever.
It may have shifted some debris in the fuel system or tank but really needs to go on a Lexia to see where the problem lies.
cheers
Paul

[Mandrake]

There's no way that higher octane alone would hurt an engine or make the performance worse.

The V6 in an early C5 (ES9J4S) is optimised to run on 98 octane anyway, although it will run on 95 octane thanks to the knock sensor retarding the timing a bit.

Octane isn't the only difference between fuels though, there are a lot of other additives that vary in quantity and quality between brands of fuel, or you could have just got a bad batch of fuel. (unlikely though) Do you normally use Shell 95 octane or a different brand altogether ?

It's probably a co-incidence unfortunately. That engine is coil over plug and renowned for coil failures, if its running really roughly and really down on power it could be a failed coil. Best thing to do is get it on a Lexia because I believe the ES9J4S has a misfire monitor that will report any misfiring and which cylinder(s) it's occurring on.

If you do have an ignition misfire you could very quickly (days, weeks) destroy one or more of the catalytic converters so I would get the Lexia scan done with some urgency as a replacement cat is very expensive! In the meantime drive with a light foot so you're not risking pumping a lot of un-burnt fuel into the cat...

[Quackers]

Thanks for the replies, looks like its back in the garage next week

Normally just use the local Sainsburys station with 95 unleaded.

Did have a coil pack go in injector 3 last year, but this feels different, seemed more normal again this morning. The annoyance of having to get a lexis diagnostics again at the garage.

Was hoping it was just a fuel issue with a repeat of something like this http://royaldutchshellplc.com/2013/04/2 ... r-engines/" onclick="window.open(this.href);return false;

[isisalar]

If you've been using supermarket fuel historicly and it now seems to be running better it could well be that the detergents in the V power have shifted something. If the eml has gone off, or it's no longer in limp mode I'd be inclined to give it a good thrashing, say 4000rpm for at least 10miles.
There are a number of members with Lexias who will be able to do a diagnosis, possibly for beer tokens. There is a list on the site somewhere.
Best of luck with it.
Cheers
Paul

[Hell Razor5543]

Here is the list of Lexia owners willing to help out;

http://www.frenchcarforum.co.uk/forum/v ... 19&t=29178" onclick="window.open(this.href);return false;

[Quackers]

Turned out it was ignition coils, but felt different this time because 4 had failed not just 1 like last time. Getting the remaining 5 changed at local independent as i did not see the point in having 5 new and 1 old in the engine as its only a matter of time until that remaining one goes.

[Mandrake]

How did you confirm its the coils ?

[Quackers]

Just bit the bullet and drove it to the garage they connected lexia up , showed 4 at fault , all changed now sounds correct idle and up to 3000 revs then it just dies past 3000 revs . Weirdly computer says nothing wrong now , no engine management fault so it's got them baffled. They think the cam might be out of sync. Might start to get expensive

[addo]

When it dies what does your MAP reading show?

[zs&tas]

blocked exhaust ? or bad timing ?

shell fuel is awesome and should make your v6 scream !