1.6 FSI - What if it wasn't run on 98RON

J

james.mckenzie

Member
Hello all,

I'm off to look at another FSI this weekend. Its a 2 owner car with under 80k miles. Looks like intake and death pipe has been sorted already which is a good start. Hope to go Proboost after purchase.

My concern today is that most folk don't realise these need to run premium fuel. If the FSI hasnt been run on premium, what actual damage occurs? What actual faults show up?

Surely folk have walked this path before as the old days of treating a car properly and actually maintaining a car are long gone. Cars are whitegoods these days.

Thanks very much for your help!

James
 
One issue could be degradation of any component that is sensitive to the alcohol content of E10 if it has been run on that since it was introduced?

If it was before that transition, isn't the main issue loss of performance and economy (bearing in mind also that running it on the cheapest supermarket fuel may also introduce other problems with crud from the tankers etc. - we had an issue locally with diesel contamination of super-unleaded in at least one local supermarket chain ~20 years ago caused by the tankers not being cleaned out between different loads that caused chaos with a lot of newer cars breaking down).
 
Thanks Robin, I hadn't thought about pre and post E10 introduction. If Ethanol is the primary cause of degradation, then it is possible only a 2021 onward problem that may affect rubber/silicone components. I guess its the structural damage I'm primarily worried about but any experience is greatly appreciated.
 
that's the issue - I don't have an FSi, the above was purely pulled from the air of recent discussions by people who really know their stuff with the model who hopefully will come in with more comprehensive advice soon.

As for everything else, it's a 20+ year old car, so despite the above maintenance observations there may well be bits of suspension / brakes etc that need to be fettled as with any A2. Best of luck!
 
Cheers Robin. Just got the reg. LY03 LZH. Seems like its had the EML light on for years.....but an engineer has got hold of it. He says... Inlet manifold Vacuum valve repaired and position sensor replaced, so no EML or problems with swirl flaps. New Expansion tank. New Thermostat & Housing.
 
We don't know why Audi have stated all FSI engines, not just the A2 one, are not compatible with E10.
The rest of the FSI engine construction, and the materials used are no different from more ordinary engines. I can't think that fuel hoses, for example, on the FSI are any different from other petrol engines of the time.
My own theory, no more than that, is that it's the exhaust system. The FSI has one C0 cat, directly after the exhaust manifold, where the down pipe would be, and a second, NOx cat further back. This setup is, or was at the time, unique to the FSI, (I believe). The cats themselves, and the combined post cat Lambda and NOx sensor are my prime suspects, not least due to the hygroscopic nature of E10. Especially on short runs, and the fact that the thermal efficiency, when using low octane fuel, means the engine will run cooler than it is designed to
The FSI was designed to achieve a very high thermal efficiency, that's why Audi specified 98/99 Octane fuel. The engine runs at a higher temperature, and has a high compression ratio, so high octane should be de rigueur. Using lower Octane fuel will not give that thermal efficiency, so combustion will be less complete, and the ECU will adjust the timing to prevent pre-ignites, so engine efficiency is reduced.
Like all modern engines, there's an EGR, which mixes some of the exhaust gases, along with the oil condensate from the PCV system, back into the inlet. If fuel, and oil quality, is poor, then that mix of volatile compounds from the crankcase, and soot from the exhaust then flow across the inlet flaps, and form a sticky varnish like accumulation. Flaps seize, actuator breaks etc.
Off course, all of this can be repaired, and if done properly, there is no reason why the engine can't be in good fettle.
Realistically, many, maybe most, FSIs will have not have been run on 98/99 Octane, (A2OC Members excepted). So finding one that has run exclusively on 98/99 is very unlikely.
So if you've set your mind on an FSI, buy with your eyes open, and be prepared to do some reparation, even if the vendor has already done so.
A fault free scan report, is only useful if it was run after an extended drive, with varied engine speeds, and loads. A scan run in a workshop is of very limited value.
A good FSI is a wonderful car. It might need a bit if effort to get is there though.
All of the above is my belief, not necessarily factual.
Mac.
 
james.mckenzie said:
Crap fuel retards timing and flags the EML. Is that what you are saying?
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I think there's a bit more to it than that.
Yes, the ECU, (any ECU), will adjust timing to avoid engine damage, if the combustion takes place too early, that's what the knock sensor is for. Usually caused by poor quality, (crap), fuel being used, that's true on any modern engine.
An EML will only be triggered if the engine sensor data to the ECU, (any ECU), indicates that emissions are likely to be higher than they should be. This is the case with any engine that is fitted with an emissions control system, (typically a catalytic converter). Same goes for diesel engines too.
Most car petrol engines are designed to run on 95 octane, unleaded fuel. The FSI is designed to run on 98/99 Octane super unleaded fuel.
Mac.
 
PlasticMac said:
I think there's a bit more to it than that.
Yes, the ECU, (any ECU), will adjust timing to avoid engine damage, if the combustion takes place too early, that's what the knock sensor is for. Usually caused by poor quality, (crap), fuel being used, that's true on any modern engine.
An EML will only be triggered if the engine sensor data to the ECU, (any ECU), indicates that emissions are likely to be higher than they should be. This is the case with any engine that is fitted with an emissions control system, (typically a catalytic converter). Same goes for diesel engines too.
Most car petrol engines are designed to run on 95 octane, unleaded fuel. The FSI is designed to run on 98/99 Octane super unleaded fuel.
Mac.
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Mac, lets say I pull the trigger on this car. Is it worth running injector cleaner and or fuel system additives for the first few tanks to assist in carbon deposit removal? Run it hot and hard etc. Id then go around the exhaust system and systematically replace aftertreatment sensors and the go ProBoost for longer term confidence. Thoughts?
 
james.mckenzie said:
Mac, lets say I pull the trigger on this car. Is it worth running injector cleaner and or fuel system additives for the first few tanks to assist in carbon deposit removal? Run it hot and hard etc. Id then go around the exhaust system and systematically replace aftertreatment sensors and the go ProBoost for longer term confidence. Thoughts?
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Won't do any harm, and will clean the injectors, and exhaust system. But if the flaps are dirty, won't help, as the flaps are well before the injectors, which are in the combustion chamber.
I'm not a fan of ProBoost, unless you have a problem, particularly with the flaps, and don't want to strip the manifold down to fix them.
There is, in my opinion, a likely downside to running an engine designed to run, (most of the time), at around 110 C, at around 90 C.
ProBoost did originally have a real advantage, as it allowed the use of 95 octane, with significant saving in fuel costs, but with the introduction of E10, and the engine being non compatible with E10, that advantage is lost.
This is, I must emphasise, only my opinion.
As with all things, take the time to research what the ProBoost map would give you, and then decide if it is right for your FSI.
Mac.
 
PlasticMac said:
I think there's a bit more to it than that.
Yes, the ECU, (any ECU), will adjust timing to avoid engine damage, if the combustion takes place too early, that's what the knock sensor is for. Usually caused by poor quality, (crap), fuel being used, that's true on any modern engine.
An EML will only be triggered if the engine sensor data to the ECU, (any ECU), indicates that emissions are likely to be higher than they should be. This is the case with any engine that is fitted with an emissions control system, (typically a catalytic converter). Same goes for diesel engines too.
Most car petrol engines are designed to run on 95 octane, unleaded fuel. The FSI is designed to run on 98/99 Octane super unleaded fuel.
Mac.
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The EML can be triggered by all kinds of errors, not all necessarily emissions-related. As for octane, from the original Audi press release for the A2 FSI:

“Multi-fuel capability

The FSI engine is designed to run highly efficiently on 95 RON unleaded and 98 RON super unleaded fuels, but for ultimate ‘lean burn’ performance, sulphur-free or ultra-low sulphur fuels are recommended.”
 
That was pre E10, with 10% alcohol.
This is more recent, from Audi Poole website:
Mac.
Screenshot_20240504-150050.png
 
Philip said:
...

“Multi-fuel capability

The FSI engine is designed to run highly efficiently on 95 RON unleaded and 98 RON super unleaded fuels, but for ultimate ‘lean burn’ performance, sulphur-free or ultra-low sulphur fuels are recommended.”
Click to expand...
Good Afternoon,

Not quite what it says in the handbook.

1714832308245.jpeg


There is a mention of 95 RON but in the context of only in emergency for a short time and fill up with 98 RON as soon as possible.

Andy
 
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Reality is virtually no FSI-engined cars will ever have been run exclusively, or even mainly, on super unleaded. VW and Audi knew that, and were absolutely not going sell a car that 95 RON would damage. That doesn’t mean that higher octane fuel isn’t of benefit.
 
Philip said:
Reality is virtually no FSI-engined cars will ever have been run exclusively, or even mainly, on super unleaded. VW and Audi knew that, and were absolutely not going sell a car that 95 RON would damage. That doesn’t mean that higher octane fuel isn’t of benefit.
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At the time it was made, and sold, you're right, 95 octane would not do serious damage to an FSI, as the anti knock in the ECU would adjust the timing to prevent it.
Fast forward to 2021, and 95 octane became E10, now with 10% alcohol. It's that 10% alcohol that's the reason that an FSI must not be run, (except in an emergency one off situation), on 95 octane E10. Nothing to do with the octane rating.
Mac.
 
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The E10 is very much a killer now. However continual use of old 95 Ron fuel must have a detrimental effect on the fuel stratification mode. Now if all servicing / repairs were carried out promptly with OEM quality part then they is a better chance of no long term damage. However do not know what sort of condition the valve gear would be in.

The end of the day Audi sold the car to be used only on premium fuel, all owners were explained this at the time. What others have done since is not only operate the car outside its design parameter but shortened its life all to save a few quid. Ironically the ones that save are not the ones now trying to resolve the issues. Do not buy an FSI as a cheap run about nor buy one that previously was used as one. At least go in with your eyes open and expect to dig deep as needed. Also remember a Proboost ECU does not allow you to run any fuel.
 
PlasticMac said:
At the time it was made, and sold, you're right, 95 octane would not do serious damage to an FSI, as the anti knock in the ECU would adjust the timing to prevent it.
Fast forward to 2021, and 95 octane became E10, now with 10% alcohol. It's that 10% alcohol that's the reason that an FSI must not be run, (except in an emergency one off situation), on 95 octane E10. Nothing to do with the octane rating.
Mac.
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… which is nothing to do with what was written in a press release or the handbook twenty years ago.

The idea that E5 95 RON is/was going to kill the engine is a bit of a nonsense - the most common FSI-specific engine problem is likely the operation of the manifold flaps, and I’m pretty certain octane rating isn’t a factor there…
 
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