Hello to everyone from a bitog user (http://www.bobistheoilguy.com/forums/),
Same here. I own Nissan Pulsar with 1.2 DIG-T engine and my manual only specs 5W-40 ACEA A3/B4 oil. No mention of ACEA C* oils. I think our engine is quite hard on oil and that's why Nissan specs Full SAPS oil (A3/B4): it has a plenty of ZDDP additive as well as high HTHS viscosity which is typical for A3/B4.
The 5W-40 is chosen over 5W-30 is probably due to the presence of turbo and the fact the it runs quite hot. Personally, I would not use ACEA A1/A5 or C oils in this engine because:
1. A1/A5 has a lower HTHS viscosity than the A3/B4
2. It is a tappet engine and the cam lobes push directly on valve pushers, so it would be nice to use Full SAPS oil in this application with plenty of ZDDP
3. Most of lube adbisers I check (Motul, Castrol, Shell) recommend 5W-40 A3/B4 with MB 229.5 spec (one of the most strict specs in the world)