[cmiovino]

With my 2004 WRX I've had the last 11+ years, I've always used 5w-40. The EJ205 is rated for 5w-30, but it's common knowledge by now that 40 weight is the oil to use, even for daily driving. It offers a bit extra protection and likely helps against oil leaks over time (maybe?). Back in the day, people would run 5w-30 and the turbo would "shear" the oil down to act like a 20 weight. Engines would spin bearings. The 40 weight would typically shear down to act like a 30 weight over 3-5k miles, and generally you'd be fine.

Keep in mind this took years for people to figure out with trial and error. We're about 10 years in with these FA20's and now the FA24. I suspect in the future it will be common knowledge to be running 5w-30 in both.

Given that, I've stuck to 0w-20 so far in my 2017, but plan on going to a 5w-30. I think going up two grades to a 40 weight is a bit overkill and there could be tighter tolerances and oil passages that 30 weight might be better suited for. Going up one step to a 30 shouldn't be too nuts.

For you winter-climate folks, this applies to you too. The first number probably should be 0 with the new FAs to keep cold starts in freezing temps the same as stock. The second number only applies once the oil is warm, which shouldn't come to play for winter street driving. The engine should be ~200 degrees, so outside temperatures shouldn't really be affecting this.

Just my 2 cents.