The consensus is that it is not the optimal oil in a climate zone that does not have low or very low temperatures all year round. Especially when it concerns more powerful cars used as intended and / or regularly moving at high speed on highways for a long time.
Time will tell if these motors will last longer than the end of the warranty. My i20N engine will run 0w30 and after modifications (Stage 1) 0w40 oil.
Maybe we need to open a oil discussion thread after all.
If the "general consensus" is various forums where people with partial knowledge or empirical understanding from technologies used decades ago , rather than reliable sources based on the science it should be the way to reach conclusions.
The engine needs lubrication in two conditions : when it's 'cold' at the startup and when it is at the operational temperatures.
For the cold start the rule of thumb says to aim for the lowest possible grade available. If we want to be really picky here, the low grade in every oil is marked for 40oC , so trying to start the car at zero degrees with a 0w oil is generally better than a 5w but if the place the car is rarely see temperatures that low , then it doesn't makes a huge difference. The start/stop system doesn't count as 'cold starts' as most are engaged only after the engine worked for few minutes and is warmer than the ambient temperature.
When it comes to operational temperatures , is when things get messed up and wrongly understood ideas becoming advices. An engine in normal use (normal use is also sporty driving or the occasional couple rounds in a race track), brings the engine to it's expected operational temperature which is around 100oC or a bit more. That's valid regardless if outside ambient temperature is 10oC , 30oC or 50oC , the car is practically a sealed system maintaining that desire operational temperature. The engine was designed and tested to run with specific grade of oil for that.
Let's assume that we want to challenge that , we don't trust the car company and we believe it's done only to present that itsy-bitsy slight fuel economy a lighter oil will give. Who can give reliable inputs that running a different grade of oil is better for that specific car and that specific engine ? Unless a car was run with the different grade of oil for 100k+ or 7-10 years , it's engine was dissembled ,checked and proven that had less wear , then I don't see how someone, anyone can claim that they know better that the company who build it and tested it in the freezing winters or the dessert heat in order to be able to give their 5-7-10 years warranties.
Tuning and do race events is a completely different story and each can consider their best knowledge or assumptions - I said that before. When it comes to normal use, long term reliability most people should really follow what is advised by the manufacturer the rest of us should avoid simple statement of dismissals that can confused owners or make them do something that can eventually hurt them.
Lastly, I hope that I don't sound too critical or harsh , I don't intent to insult anyone but I can't find a softer way to explain what I wanted to say and stress out how we should provide advice and opinion for various matters.
