Fiat 9.55535-GS1

[RedemP]

Does anyone know what the Fiat 9.55535-GS1 spec stipulates apart from ACEA C2 and SAE 0W-30? Thanks.

[Colin Edwards]

https://www.oilspecifications.org/fiat.php

Given it relates to a specific oil viscosity (relatively low) it probably mandates a high viscosity index and low Noaks volatility rating.  A very high spec oil!
The high viscosity index means is shouldn't lose much viscosity when hot and a low volatility rating (%) means the oil will evaporate less when sprayed up onto the base of the piston crown.  High output direct injection engines featuring oil cooled pistons (like the Alfa Multiair) will evaporate a fair bit of their oil, with a lot of it ending up on the inlet valves if the Noacks % is too high.  Fair chance this Fiat spec goes some way to addressing this issue.
The multiair in my Abarth uses almost no oil now that I use a Fiat 9.55535-S2 compliant oil. 

[RedemP]

Thanks Colin.

Would there likely be exclusive additives stipulated/used to drive down volatility beyond levels already in a multi spec C2/C3 oil?

My suspicion is that when they went from Fiat 9.55535-S2 (C3) for the first generation MultiAir to Fiat 9.55535-GS1 (C2) currently was almost entirely driven by the desire for increased fuel economy from the C2 base as HTHS viscosity is the only major difference between a C2 and C3, barring any exclusivities.

[Colin Edwards]

Methinks the chemistry of a Fiat 9.55535-GS1 compliant oil would be fairly complex, however nothing stopping a major player reverse engineering it to gain Fiat approval.  Fiat would probably want as many manufacturers as possible to produce a compliant oil - ensures an engine friendly oil is readily available!  I wouldn't even begin to guess at what alchemy is needed to lower oil volatility!

Agree the lower viscosity oil will greatly improve engine efficiency, reduce drag and lower emissions.  Fiat, like any other manufacturer needs the oil companies on-side for meeting design rules.  Need everyone concerned pulling in the same direction to ensure as much oil as possible stays INSIDE the engine!