The simplest way to post this is to paste the emails between myself and Shell. Shell have started to get all technical on me, so I welcome advice as to my next course of action. My emails are in bold type:

Dear Sirs

I have been using Optimax regularly for a few years now (pluspoints no. xxxxxxxxxxxx). Last week my engine warning light flashed on approximately 5 times. I immediately had my car looked at by my local dealer (xxxxxxxx). Their first query for me was which fuel I was using and that I should change as this had led to some det (they mentioned a figure of 8% ?). However, they told me that my ECU had no fault code & that my car (Impreza WRX, 2001) appeared to have corrected itself.

I always fill up with Optimax in the belief that I pay the extra for a cleaner engine & it will help avoid problems like det, so I'm sure you can understand how disappointed I was to receive the advice I got from Subaru & am now confused regarding the best option for fuelling my car. For your information, I almost exclusively use your service station on xxxxxxxxxxxxxxx.

I would be interested to receive a response from you on this matter.

Regards


Thank you for your recent e-mail.

I forwarded your enquiry to Shell's Fuels Technical Manager. They have asked to clarify if you refer to deterioration or detonation with the term 'det'. This will assist with their investigation and answer.

Yours sincerely,



Thank you for your reply. I have enquired further with the technician who inspected my car and he tells me that my car had suffered from detonation. Subaru use their in-house scale to measure detonation. A measurement over 2.5% is considered to be abnormal; 9% would put the car into 'limp-mode' requiring urgent attention. My car's detonation was measured by Subaru to have reached 8%.

I hope this is useful for your investigation and if I can be of further assistance please do not hesitate to contact me.

Regards



Further to your last e-mail, please find attached the response from Shell's Fuels Technical Manager.

"We are very surprised to hear of the problem that you have had.
Detonation would usually a symptom of either low Octane (RON), carbonised deposits on the inlet valve or a faulty EMU.

For your guidance, Optimax fuel in the UK has an RON of 98 or higher and we have had no other complaints on Optimax. We also routinely check our retail site fuels for quality and those results do not show any sub 98 RON values.

We would anticipate that your vehicle, as well as most modern EMU equipped engines, would have a knock sensor (detonation). This sensor allows the EMU to adjust the ignition timing of engine to suit the prevalent fuel and the driving conditions. This is the reason why modern vehicles can capitalise on higher RON fuels and gain increased acceleration and power.

I am not sure whether your vehicle manufactures recommended the sole use of high (>97) RON fuels, but given the EMU and Knock Sensor point above, it would not surprise me that you could run on regular 95 RON fuel without suffering any adverse effects to the engine, apart from a loss of acceleration and power. I should say that this is not a recommendation and that you should check with the OEM first before changing your fuel, but I am merely making the point that it is very likely that the engine is designed to run on fuels with different Octane levels.

As to carbonisation, as you may know the Optimax fuel has a high level dose of detergent additive that not only prevents carbon build up, but also actively removes it should the vehicle have any from previous different fuel use.

We would recommend that you consult with the OEM as to whether the vehicle does indeed have a Knock Sensor and what RON rating is recommended for the fuel.

We would be happy to assist you further, but we do not believe the problem that you have to be due to the fuel."

Kind regards,

 

lol, they should ask their 'technical manager' that if the car didn't have a knock sensor, how the f' would it know it was experiencing 8% knock???

 

is it possible the knock sensor is FUBARd? cos the guy does kind of have a point about the management system being able to cope with different octane fuels....

 

Is your car standard ? Has it been remapped ? Were you doing anything different with it (dyno, racing etc)

Andy

 

Simple answer. Get a sample of the petrol and get it tested.

Without doing so you'll be playing letter tennis all year

FWIW, I have had a bad batch of optimax on one occasion. I put it down to the pumps not being used anywere near as much as Normal unleaded, so the fuel is left to stagnate in the tanks.

 

Standard car, apart from cat-back exhaust which I have had on for about 3 years. The engine light flashed as I was driving very steadily- either in or just entering a '30' zone. Immediately prior I had been driving steadily on a '60' B Road.

I had put it down to stagnant fuel; a 'bad batch'- but am still surprised this would deteriorate so much with a 98+RON.

I've not had any problems before using Optimax from the same garage all the time- I guess it could always be possible the knock sensor is faulty? But then would I not have had a fault code on the ECU or had more dramatic problems by now?

 

If you had no problem with the same fuel from the same garage just prior to it can't be bad fuel, least not stagnemt, you have a problem with something on the car, maf, knock sensor itself, coolant temp sensor maybe, lamdba sensor maybe.

Lean running will cause the ecu to pull back off boost (on cruise).

You are also assuming Shell are fully familiar with your vehicle (ie the Impreza if thats what it is), which that obviously can't be since they make fuel not cars iyswim.

So suggest stop worrying about the fuel and get a second opinion from a dealer that can do more than just read the select monitor.

You haven't mentioned your car's model year and type which is always helpful btw.

cheers

Bob

 

Thanks for the comments Bob. I appreciate your interest- as with other posters on this too.

I made no assumption that Shell would know anything about an Impreza- I told them the car's basic details & who the dealer was in case they wanted to verify what I was relaying to them. If and when they wanted more detail then I would give it.

In my original post (within the copy of my email to Shell) I have mentioned the car's model, year and type.

Presumably the faults you suggest as possibilities would not show up as fault codes? If not, do they need individually testing by a dealer?

When I suggest stagnant fuel- I meant that possibly this was a one-off batch that had spent longer in storage than has been usual? But of course I am guessing and lack your technical knowledge.

To clarify, my entire experience of any problem here was that my engine warning light flashed on & off approximately 5 times. Hasn't happened before or since. I have not felt any problem with the car, but it obviously concerns me.

 

Bexlee, you still haven't told us what the make/model is.

UK/EU/JDM ?
MY?
Model?

If your ECU has detected knock (detonation) then there are several possible causes, fuel quality being just one of them. For such faults the dealers have fault analysis charts to help them isolate and identify the cause. Did your dealer go through the full fault diagnosis process to eliminate all the other possible causes? If not then I suggest that's the first step as just guessing the cause will not be a productive use of anyone's time, yours included.

 

Is it me or has noone read the origional post??

Impreza WRX MY01 !!!

 

Had some KL activity recently and it was definately down to a bad batch of Optimax.

Used a different garage to my usual two and didn't really think about it being the fuel until someone suggested I add some extra OB. When I undid the filler cap I got a strong wiff of diesel..! Needless to say adding the OB improved things (reduced ~50%). After running till almost empty and refilling at my usual garage (that sells a lot of Optimax due to it being very reasonably priced and therefore you can REALLY smell petrol when filling) it had returned to normal.

FWIW I recon that the garage I used had recently swapped tanks from diesel to Optimax and it hadn't been completly drained.

Where is PS Lewis and his insistance that a KL is a waste of time..?

 

Apologies, must have been

 

I dont think they are allowed to swap different types of fuel tank to another one, especially diesel to petrol.
Probably more likely that diesel was put into the petrol storage tank by the tanker driver or an error was made at the fuel depot and diesel put into a petrol section of the tanker.

Tony

 

Ah.

Possible.

My father in law used to drive tankers and said he regularly put white diesel into his lorry's compartments where red diesel had been.

He said there was always a puddle of red left as they could not be fully drained.

Possible to mix fuels then.

Bexlee,
buy a volvo,
less complicated!

Ted.

 

In October I got home from work (ten weeks abroad) having left about half a tank of optimax in the car for the whole period. I thought that would be better than running it on normal stuff as optimax isn't available near mums garage. However for the next two days the car frequently lit up the knocklink like crazy under WOT at 4000rpm. Two weeks later after running normal U/L it hadn't improved. Then I got back to civilisation and filled up with fresh optimax. Lights dissappeared within a day. Was told a week later or so that Optimax is not that RON stable over time and loses some oomph, hence my knocking activity

 

He still hasn't said weather its a UK or import though

 

All fuel starts to deteriate from the moment it's refined. There was a thread about it a while ago about it and you'd be supprised by how much and how quickly it happens..!

Every wondered why the motor mower won't start after being in the shed over winter, yet when it was put away it worked fine..? Drain the fuel tank and lines, fill with fresh fuel and it'll start straight away..! That's why Emergency generators in hospitals ect.. don't have fuel in their system and have to be primed. The fuel should be refreshed all the time whilst on stanby.

 

He can tell you it is a UK car- hope that will help you in forming your comment. BTW, how is the weather in Teesside, leonpoole? I shall be up there on Sunday for the Boro!

Responses so far seem to either strongly suggest the fuel could have deteriorated, or strongly suggest that it can't be the fuel at fault and it is likely to be a fault with either maf, knock sensor, coolant temp sensor or lamdba sensor. I shall put this to my local dealer.

Incidentally, I have filled up with Murco's Super Unleaded since this (the garage location is more convenient for me than Shell too) and the car has felt more responsive on the throttle- I have considered the possibility that this is just a placebo effect, but I think it is more than that.


Thanks for all the considered comments on this.

 

The weather is crap up here as usual

 

I am not a techie, but would like to add my bit with regards to shell.


Several years ago I worked for the AA printing. We printed 95% of the technical departments stuff. There were 2 occasions when Shell fuel was not as it should be.
1. A members car broke down. The AA was called out, but could not rectify the fault at the road side. This car was relayed & ended up in the Technical workshops. To cut a long story short, the problem was the fuel. It was found to have approx 5-10% of cleaning fluid in the tank (memory not so good).
The AA took Shell to court on behalf of the member. I think that Shell settled out of court & paid for all repairs etc.

2. Shell were in court for the octane rating of there fuel (or lack of). It was a big case with loads of legal jargon & contravention of laws etc. This was not the AA it was a more public case. They eventually got away with it. This was because the average octane rating was 0.00001 above the published spec. There were times it was below the rating, but oil companies have more money than Governments.

I never used Shell for years & have only tried in my Scooby a couple of times. These did not lead me to think it is worth the money.

 

Has your warning light thingy come on anymore Bexlee?

Ted.

 

When the warning light flashes like that its because a sensor has exceeded its predefined limits ie closed loop at max plus or max minus for a long enough time, thats why I suggest getting it checked more thoroughly, I've had Optimax sat in my tank for 6 months without starting the car, when I did it was fine, no problem at all.

My point for posting was that you should look harder at the car and not focus on the fuel, if there is an issue with the car it may not store a code, a warning doesn't always, if maf limit is exceeded for example, still need to know the Model year, if its new age then fueling issues will show up as misfire codes soemtimes for example.

Bad fuel is always a possibility ... thats why a Knocklink is a good idea for any of these cars.

The more we know the more we can help.

cheers

bob

 

Hi Bob

As you have posted....... I'd look at the car and not the fuel !!

I just thought I would add that My MY01 Bugeye has a Knocklink and it kicks off from time to time.......including the time I put in some BP ultimate Sorry Bob !

At no time has the CEL light flashed or stayed on suggesting that det is the problem.

Cheers

Shaun

 

Nothing at all since; no signs of problems driving the car.

Thanks for your continued interest- I do appreciate it.

Everything I know is in what I have already posted. Before I put the points raised here to Subaru, I really don't know what I can add. If there are things I am not covering, please ask & I'll try to answer.

 

UK car

 

The 01 WRX will adapt very quickly from Optimax to lower octane such as 95ron. Depending on the driving style it may still det initially until the ECU resets its knock parameters (thats what you would be seeing on your K/L Shaun)
If after adjusting to the lower fuel octane the engine was still knocking and the ECU had done all it can in way of additional fuel, reduced ignition timing and lowering boost, then you would get a CEL.
It is possible, on 01/02 WRX specifically, to get a misfire flashing CEL if the ECU pulls the timing back so far that the engine does actually misfire !
If indeed you had 8 degrees of stored memory retard then a misfire is highly likely.

Andy

 

Thanks Andy .F- though just to clarify, I had been running on solely Optimax for years.

 

I was just thinking maybe they had filled the optimax tank with 95 I'm sure it happens ....... and I'm not so sure they would admit it and pump it all out again !!

 

If the ecu retarded that much it would drop boost, suspect its related to lambda, the sensor is probably "failing" but not enough to show a permanent code, try driving on steady throttle at say minus 0.15 bar vac and see if you can induce a cel, if a GC8 drive on 0.4 bar at steady throttle and let revs rise over several minutes, that will show a dead lambda.

bob

 

I ran out of Optimax options a couple of times on MY00 UK and had to fill up with 95 RON - it brought the CEL on every time while the ECU adjusted itself, then went away. Cut boost etc....

Its quite concievable that you either filled up with the wrong stuff, or they labelled the tanks the wrong way round?

MB