DS3 DSport THP155 - Changing to higher octane fuel

[DannyDS3DS]

Hi Club Members,

I'm picking up a used 2012 DS3 DSport THP155 tomorrow, it has 35k on the clock and i believe since day one the previous owner has ran the DS3 on standard 95 Octane fuel.

I'm going to make the change to Super Unleaded or possibly V Shell/Momentum99 but because the car has has 95 octane in it from day one, will I experience any performance/mechanical issues while the engine adjusts to the 98> octane fuel?

Thanks!

[lfcrule1972]

I don't believe you will, although I've read on the forum (in previous posts) that the ecu will take up to five fill ups to properly register the new fuel type.

Given that a lot of drivers use any and all petrol stations I don't expect you'll notice this though You should eventually feel an improvement in the way your car drives if the advertising guff is to be believed.

[Superfly Guy]

I suspect the valves will be suitably coked up with 95 fuel and that mileage if it hasn't been walnut blasted or decoked within the previous 5-10k miles. If that is the case then changing fuel wont make much difference in noticeable performance as you will already down a significant amount of power.

[lfcrule1972]

I forgot about that, will need to get it walnut blasted either at somewhere like SP Tuning (Jamie is here on the forum) or else a local provider of that service.

[DannyDS3DS]

Thanks guys, I'll look into whether this has been done or not! My brother used some kind of petrol additive on his JCW to "clean the engine" is this something that could be used as a cheaper but slightly less effective way to walnut blasting?

[lfcrule1972]

I don't think so as the additive/cleaner applied in this way doesn't reach the correct parts of the engine/valves etc.

Have a search for walnut blasting on the forum (top right of the page) and look at previous posts on this for more info.

[Chris_Blue]

^ LOL. From a diesel owner.

You could try the Terraclean Induction cleanse- theres a blog on it on this site
Might do the trick- bout £100, but make sure you get the clean they reckon deals with the inlet valves

Additives don't clean the inlet valves, altho the fumes may help, but additives will clean several other parts and sensors

Give it a good thrashing will help

Nothing will resolve the inlet valves clean issue- just an attribute of the GDI engine.
Trick is, to get the cheapest and effective cleanse

[lfcrule1972]

I read a lot of posts on the forum Chris, even the petrol ones, I'm not a fuel racist !!! ha ha

[DannyDS3DS]

^ LOL. From a diesel owner.

You could try the Terraclean Induction cleanse- theres a blog on it on this site
Might do the trick- bout £100, but make sure you get the clean they reckon deals with the inlet valves

Additives don't clean the inlet valves, altho the fumes may help, but additives will clean several other parts and sensors

Give it a good thrashing will help

Nothing will resolve the inlet valves clean issue- just an attribute of the GDI engine.
Trick is, to get the cheapest and effective cleanse

Cheers for the info Chris! I did see some info about Terraclean, i'll look into it some more!

And don't worry, i'll be giving it a real good thrashing! Haha.

Yeah, it's just how they're I guess. No engines perfect!

[Saintsteve]

Don't waste your money on Terraclean .... If tried it, waste of money.
If under warranty , if it's stuttering under hard acceleration , get the dealers to remove the cylinder head for a decoke.

Cured ours with a lot less mileage then your 35k... I've always run our ds3 155thp on super for the past 6000 miles

[Nomgle]

I suspect the valves will be suitably coked up with 95 fuel...

The carbon buildup is created from oil-vapours - it has nothing to do with the fuel's octane rating in a direct-injection engine. The fuel is injected directly into the cylinder - the intake air and oil-vapour have already passed (and deposited on...) the valves by the time they first meet petrol. It's for this reason that in-fuel-tank cleaning products won't do anything to help.
On an older engine design, there is arguably a case to suggest that "better" fuel could do a better job of cleaning the valves as it washed over them - but we don't have any fuel washing over our valves.

[Superfly Guy]

The carbon buildup is created from oil-vapours - it has nothing to do with the fuel's octane rating in a direct-injection engine. The fuel is injected directly into the cylinder - the intake air and oil-vapour have already passed (and deposited on...) the valves by the time they first meet petrol. It's for this reason that in-fuel-tank cleaning products won't do anything to help.
On an older engine design, there is arguably a case to suggest that "better" fuel could do a better job of cleaning the valves as it washed over them - but we don't have any fuel washing over our valves.

Those more knowledgeable may suggest otherwise.

[cameron20020]

The carbon buildup is created from oil-vapours - it has nothing to do with the fuel's octane rating in a direct-injection engine. The fuel is injected directly into the cylinder - the intake air and oil-vapour have already passed (and deposited on...) the valves by the time they first meet petrol. It's for this reason that in-fuel-tank cleaning products won't do anything to help.
On an older engine design, there is arguably a case to suggest that "better" fuel could do a better job of cleaning the valves as it washed over them - but we don't have any fuel washing over our valves.

While I agree with you most part, i disagree that higher octane fuel will make no difference. One mechanism through which the carbon/oil deposits cause detonation is by effectively lowering the octane of the combustion chamber contents before intended spark ignition. My theory is that having a higher octane to start with may mean more deposits are required to cause detonation. Seems to make a little bit of an un-scientificly proven difference on mine.

[Nomgle]

One mechanism through which the carbon/oil deposits cause detonation is by effectively lowering the octane of the combustion chamber contents before intended spark ignition. My theory is that having a higher octane to start with may mean more deposits are required to cause detonation. Seems to make a little bit of an un-scientificly proven difference on mine.

Yep, that sounds reasonable. I wasn't suggesting there is zero advantage to higher octane fuel - I was just pointing out that it's not specifically going to help prevent the carbon buildup. It may mitigate the effects to some extent as you describe ... but there's still a carbon build-up problem to be addressed. And if you've run 95 octane fuel, there won't be any more/less carbon than if you've run 98.
Having said that, mitigated detonation is better than detonation !

[cameron20020]

Yep, that sounds reasonable. I wasn't suggesting there is zero advantage to higher octane fuel - I was just pointing out that it's not specifically going to help prevent the carbon buildup. It may mitigate the effects to some extent as you describe ... but there's still a carbon build-up problem to be addressed. And if you've run 95 octane fuel, there won't be any more/less carbon than if you've run 98.
Having said that, mitigated detonation is better than detonation !

Couldn't agree more.

I'm actually thinking somthing like WMI might be a better long term, low maintenance solution. As in a water methanol injection kit to spray the intake valves on boost.
Don't care too much about extra power at this point, I just don't want to have to fork out every 20,000kms or so for an intake clean, nor worry about shattered pistons (along with my hopes and dreams).
I think Ragnarok mentioned his WMI kit helped with keeping the valves clean.

Only problem is that WMI is pretty illegal in Australia, though I'd love to find an engineer who can sign off on even a water only system.