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Old 01-06-2018   #31
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Re: Twinair hesiting/misfiring when accelerating

Quote Originally Posted by Torsten S View Post
Interesting scans. That's a pretty good way to confuse the customer and the workshop crew

Since a change from 5W40 to 0W30 (or in general a lower viscosity full-synth) is a common theme in Euro6 engine adjustments, I would not assume that the 5W40 is bad for the engine and was changed because of problems, but because of tighter requirements. I'd stick to the 5W40 for the Euro5 engines - especially since Fiat seems to make it quite clear in your case that the new spec applies only to the Euro6 engine.

These tighter Euro 6 petrol engine requirements were what exactly?

You only need to be able to read letters to know there are no differences between Euro 5 and Euro 6 emission regulations for petrol engined cars, only diesels had alterations between the two regs.

Both Euro 5 and Euro 6 petrols need to meet the same levels, which are:

CO - 1 g/km,
HC - 0.1 g/km,
NOx - 0.06 g/km
PM - 0.005 g/km

Changing the oil would not have altered anything emissions wise as there was no tighter requirements to meet for this or any other petrol engine.

If it was true, why was there no difference in emission output of this engine after they became Euro 6? Same before, same after.

In fact, Euro 6 TA's still stated 5W40 in their handbooks up until April 2014, quite some time after they started selling them as Euro 6, so it's a fact they didn't need the change in oil to meet the regs.

As is well known on this forum, both earlier and later Multiair units both fail, so to actually pin it on one of the two stated specs of oil in the different versions of the handbook is quite a stretch of the imagination, though the real reasons are another discussion, the truth is out there, it probably is oil related, but level rather than which of the two spec's.

There must have been valid reasons to swap both service interval and oil spec, but they aren't due to tighter emission regulations because there just wasn't any, proof is in the tailpipe!
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Old 01-06-2018   #32
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Re: Twinair hesiting/misfiring when accelerating

Don't forget the C3 oil is low ash, the C2 being more conventional. Low ash oils have a reputation of being less protective so that could be the reason for cutting the service intervals.
PS, I too have letters before and after my name.
I'm sure others with degrees and certificates will be as well. Mine though are for electronics.

Why though are C3 oils now specified in a petrol engine? Ash can build up in a diesels DPF but if oil consumption is minimal surely engine oil wouldn't be a big issue.
Oil consumption in a FIRE engine is negligible but C3 oil is specified, perhaps then fiat thought that cat degradation could occur in the TA due to moderate oil useage in the first few thousand miles, just thinking out loud though.
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Last edited by murphyv310; 01-06-2018 at 20:24.
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Old 01-06-2018   #33
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Re: Twinair hesiting/misfiring when accelerating

The only change between Euro5 and Euro6 for petrol cars was the introduction of a particle number limit, in addition to the already existing particle mass limit. This was brought in, since the low particle emissions of modern diesel were now below those of (mainly direct injection, but many turbos had problems as well) petrol engines. Apparently it was even necessary to increase the limit by one order of magnitude over that of Euro5 Diesels for the first 3 years, as many petrol engines were not able to achieve the lower limit.

The handbook issue seems to be the one that Trevor pointed out, that the handbook had the Euro5 spec in it, with a supplement for Euro6? So it still seems that all Euro6 had the 0W30 from the start, but in 2014 there would be both Euro5 and Euro6 on the market and the handbook reflected both? Not the best thing in my book to do, because it's just bound to cause a lot of confusion.

Re letters after the name. I was pointing that out tongue in cheek, as I realised that I had gone into lecturing mode (occupational hazard). Disclaimer: I am a thermo- and fluid dynamicist, my last work on engine development was in the 90s, and even back then I was only running design tests on variable valve trains. So the intricacies of Euro5 and Euro6 are not my speciality, I rely on colleagues' expertise for that. What I do know is that in many cases a lower viscosity oil was required, in many others it wasn't really required, but done nonetheless, as there were some efficiency gains to be had. It seems to cause some problems with bearings apparently, as the load bearing capacity of the oil film needs higher pressures - and with oil consumption.

Oh, it seems I'm rambling again. Occupational hazard, see above ;-)
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Old 01-06-2018   #34
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Re: Twinair hesiting/misfiring when accelerating

Quote Originally Posted by murphyv310 View Post
Don't forget the C3 oil is low ash, the C2 being more conventional. Low ash oils have a reputation of being less protective so that could be the reason for cutting the service intervals.
PS, I too have letters before and after my name.
I'm sure others with degrees and certificates will be as well. Mine though are for electronics.

Why though are C3 oils now specified in a petrol engine? Ash can build up in a diesels DPF but if oil consumption is minimal surely engine oil wouldn't be a big issue.
Oil consumption in a FIRE engine is negligible but C3 oil is specified, perhaps then fiat thought that cat degradation could occur in the TA due to moderate oil useage in the first few thousand miles, just thinking out loud though.
Interesting point about the low ash oil. Could it be that with the introduction of particle number limits, even moderate oil burn could lead to a higher rate of emmision rate fails on that front? My handbook states 400ml per 1000km is considered normal, and I have just topped up 200ml after 620 miles, so am at about half that. Hope it will settle for less than that after the run in period.

Electronics, that's black magic :-)
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Old 01-06-2018   #35
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Re: Twinair hesiting/misfiring when accelerating

Goudrons: Agreed, there may be other reasons for the change in oil with the change to Euro6. But I'm certain they are valid engineering reasons, not a money making scheme. I just know from colleagues that there was a lot of development going on at that time not only for diesel, but also for petrol, most engines were definitely not the same before and after.

I guess that the PN limit was brought in because it is less particle mass than size that is dangerous, as it is a quite narrow band of particles that will enter the lung. Too big, and they don't reach the alveoli, too small and they will just be exhaled again. It's the ones that are just the right (or rather wrong) size that enter the alveoli and stay there. Just heard an interesting talk by HSE last week about that subject. IIRC the critical size is somewhere between 1 and 10 microns.

With that in mind, some Euro5 petrol cars where most likely worse than Euro5 diesels, as they'd have had fewer, but smaller particles and could therefore cause more lung damage.
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Last edited by Torsten S; 01-06-2018 at 20:59.
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