I don't understand why you always try to be at odds with me, I'm not your enemy, lol.
I calculated oil viscosities at freezing temperatures for the purpose of comparison. It's one metric that showcases the physical properties of the lubricant.
Many of the oils in that list can be run in the same engine. Imagine if the engine was so sensible to viscosity, when you switch from a 0W-20 to a 0W-40 the oil would not reach many critical parts, and the pump would struggle to pump it. But that's not the case, is it?
You are well within the 5W winter rating with some room to spare.
I would email Dave at Redline (PM me for the email if you need it) and ask him about the knocking noise in your HEMI during winter on 5W-30. It would be awesome if you would share his response. I'm curious what his take on it is, as he should know more about their own products than any of us here.
Both are in the same ACEA A3/B4 class of motor oils. The main difference is that Mobil 1 FS 0W-40 carries actual OEM approvals, while RedLine 5W-30 does not. For instance, a Porsche A40 approval (which the M1 0W-40) is obtained by torture testing the oil in a twin-turbo Porsche engine around the Nurenburg Ring in Germany. After the test, the engine is torn down and measurements are taken, and the oil is analyzed for oxidation, viscosity retention, soot loading, etc. RedLine develops its oils with the help of Lubrizol. These days oil development for a corporation such as Lubrizol is more of a modular exercise where they pick the additive package based on the client's specifications. All RedLine has to do is ask them for OEM compatibility like BMW LL-01, MB229.5, and so on, and ACEA A3/B4 class. If you put a few of these OEM approvals together, they cross, so it's easy then to claim compatibility with even more OEM approvals. However, RedLine does not submit any of its oils for any OEM approvals. I don't even care about API licensing, as the API is irrelevant when it comes to ACEA A3/B4 and C3 lubes.
For the US and Canada, for anyone who doesn't want to pay for RedLine or can't easily get it, Mobil 1 FS 0W-40 is a very good option. For your region, I wouldn't run anything that starts with 0W. I just looked up winter temperatures in Dubai, and 14 Celsius doesn't sound bad at all. You can run RedLine 5W-30 year-round. If you want two viscosities, then in the hottest months of the summer I would run RedLine 5W-40. If you want to run other brands, then at least 5W-40. Approved oils are blended thinner than RedLine because ... fuel economy. Mobil 1 FS 5W-40, or even Mobil 1 FS 5W-50 in the summer. Motul and Ravenol are also good options, but I wouldn't run V300 in a HEMI. They also make a V300 for race cars, but I wouldn't run that one either. Racing oil belongs in a track where it's drained after the race is over. In Australia, they run 10W-40 and 15W-40 in HEMIs. High heat + thin oil is a death sentence for a HEMI. Many manufacturers that have more common sense than Chrysler/FCA/RAM/Stelantis specify different motor oils for your region, usually higher viscosity, and explicitly prohibit the use of thin fuel economy oils.
[Edit]
@ramffml
RedLine 0W-30:
-20C -> 2974 cSt
RedLine 5W-30:
-20C -> 3146 cSt
As you can see, at -20C the viscosity difference (for sub-zero temperatures that is) is minute, not enough to cause any earth-shattering problems like knocking in an engine. I would be interested to read your rationale for the perceived piston slap/knock when running RL 5W-30.