Technical Oil weight for 1.2 16V

[Bromodo]

Hi,
I know that there are 981,342 different topics on this, however I couldn't find one that actually sums it up. The last oil change on my car (according to the service book) was in 2008, 80.000km ago - it's time, alright.

So, the manual calls for 15W40 (CCMC G4) or synthetic 10W40 (CCMC G5/ACEA A3-96 and API SJ). I think it's safe to disregard the mineral 15W40 altogether.

Fiat Lubrifianti says "Alternatively (instead of Selenia 20K Semi-synth 10W40), it's possible to use Selenia K SAE 5W-40" for the 188 (which shouldn't differ mechanically at all from the 176, other than 6HP less due to pre-cat and EFI).

For the newest 1.2 16V incarnations (i.e. Stilo or Lancia Ypsilon), it states "Alternatively (instead of Selenia 20K Semi-synth 10W40), it's possible to use Selenia Performer Multipower SAE 5W-30" instead.

The latest 1.4 16V non-turbo skips the 10W40 and get a straight recommendation for "Selenia K Pure Energy" SAE 5W-40, which is Selenia K as mid-SAPS to meet some exhaust gas standards.

That leaves the choices between 10W-40 semi-synth., 10W30 synth. and 5W-40 synth.

Semi-synth 10W-40 and synthetic 5W-40 have about the same viscosity across the board, yet the viscosity index of the 5W-40 is about 30% higher. Also, synthetic oil doesn't sludge up the engine, from which I take that 5W-40 should be the default now.

So, 5W-30, which is less viscous is only advised in severely cold climate (as in -25°)?

 

[fingers99]

I don't really get your point.

Generally, the 16v engines (which have hydraulic tappets and a higher output) need fully synthetic 5-40. 8v engines will be fine on a semi synth 10-40.

 

[Bromodo]

I don't really get your point.

Generally, the 16v engines (which have hydraulic tappets and a higher output) need fully synthetic 5-40. 8v engines will be fine on a semi synth 10-40.

Never mind, I figured that out, too. If you compare the recommended 10W-40 and 5W-40, then they have about the same viscosity in terms of mm^2/s at 40°C and 100°C. The viscosity index is higher though, and so it's just thinner when the engine is cold (<40°C). Fiat does however state Selenia K 5W-40 even for the newer 1.2 8V engines (it costs about the same anyways).

5W-30 is only useful either in severely cold climate, as while it would be better at an ambient temperature <10°C, it would get too thin in stop-and-go traffic and in the summer on the highway.

Well, I'll just order 5L of eni i-Sint 5W-40 - the spec sheet is identical to the Selenia K, but at 1/2 the price and Agip/eni Racing 10W-60 was always good to me (as in: engines >150.000mi) thus far. Should be fine.

 

[fingers99]

Don't forget that when FIAT were specifying 15-40 there was no 10-40, let alone 5-40, and synthetics were just a twinkle in some oil chemist's eye.

Anything within the spec will do just fine: the car would benefit much more from more frequent oil and filter changes than any other factor. Even the 16v engines have an extremely low specific output and are unlikely to be over stressed in anything like a standard state of tune.

 

[Bromodo]

The handbook was assembled in 1998. It states 15W-40 and semi synth 10W-40 as suitable, yet recommends "Selenia 10W40".

Selenia K 5W-40 just seems to be the modern successor to that, with the same characteristics except for being thinner when cold (<40°C) to save fuel and reduce wear on start-up.

The engineers from Alfa Romeo knew fully synthetic 10W-60 "for sportive driving" in the early 90ies already, and so did the Fiat ones in the mid-90ies (and even mandated it on the Alfa GTAs and 166 Twin Spark).

5W-40 on any FIRE engine should be just fine in 2014, though.

 

[fingers99]

But did Selenia make a 10-60 back then? Castrol and -- maybe -- a few of the bleeding edge American companies.

FIAT are unlikely to recommend anything they don't have a major shareholding in!

But 5-40 fully synth would be my choice for a 16v n/a.

 

[Bromodo]

Back when Alfa Romeo was state-owned, they recommended Agip (also "kind of" state-owned until 1992) instead of Selenia, who had a 10W-60 for some time. Actually, Agip Racing 10W-60 was literally the mandatory oil for the Alfa 166 and V6 GTAs, even if Selenia has one now, too. If I remember correctly, the 2.4 20V Stilo Abarth mandates 10W-60 as well.

I did however find the information I was looking for:

Given that most of us live North of Rome (and Selenia K states to be specifically for FIRE engines anyways), 5W-40 (API SM and ACEA A3) it is.

I still can't make sense of the 5W-30 (ACEA A5 and API SL resp. FIAT 9.55535-G1) in our climates, though:

+ "Formulated to allow a reduction in fuel consumption"

- No WOT highway driving, 130kph max. or it gets too hot
- No longer highway journeys, or it gets too hot
- No Stop-and-Go in the summer, or it gets too hot

Sounds like suburban use only.

I did also figure out what Fiat meant by 15W-40 in my manual:

South of Naples, Portugal and Greece.

 

[Bromodo]

So I got around changing the oil.

I think that even 2.8L of Diesel would be more appreciated as a lubricant by the engine than this mixture of too old 15W-40 (no, I didn't put that in there) and 10W-60 (yes, I did top up with that one).

Now I've filled 'er up with eni i-Sint 5W-40, which is like water at room temperature compared to that crap. The rough idle is gone (after 50mi), and the engine is a bit more responsive already.

Any suggestions except for replacing the oil in ~1000mi again, some magic stuff that helps getting the black tar crap out of the engine maybe?