Originally Posted by SubieRubyRoo
We all know EJs, especially in WRX/STi guise, are friendly to heavier weights. NA EJs are not really as picky.
But come on, Rand, with 14,000+ posts and all you've got is opinions? Not posts of failures in the FA-DIT series from 0W20s? Did you ever think that since this was a clean-sheet engine design, just maybe they got it right? You are being a little ridiculous to compare an Italian turbodiesel V6 in a heavy truck to a Japanese flat four in a car that's half the weight. The FA20DIT has been around for several years now, and since I don't go off of opinions, but data, I did some digging. NASIOC actually has a table of whoever felt like signing up their vehicle with a list of mods, and if there was a problem with their vehicle. On this list, only 7 of over 700 samples were completely stock cars, for a failure rate of about 0.9%. And there's no telling what the root cause failure was for those. From what I can find, in America/Canada, Subaru has sold around 130,000 WRXs since 2016, and since people are much more likely to speak up about failures rather than something that works as expected, even if we use the failure rate of 0.9% across the entire population, this means most likely a maximum of about 1,200 engine failures from all causes including plain stupidity. Since members on NASIOC are likely more vocal, and likely drive their vehicles much harder than the average buyer (including OP since he specifies mostly in-town driving), I'd expect that percentage is slightly inflated compared to reality.
Am I saying don't run a Xw30? Nope, if you want to, feel free. The manual allows for it. In fact, if you are modifying the engine with a tune and other bolt-ons, it's probably a good idea. But to spew 0W20 hate towards a new owner, with warranty, that will apparently be keeping the car stock, and no real data showing there is any real need for a heavier oil is going a little overboard. For the record, I don't think anybody with real experience on this board would consider excursions into the 230*F range even close to being excessive for a synthetic oil, especially in a car with an oil cooler.
NASIOC FA20DIT list
North American WRX sales since 2016
OP, it's your choice. Running any SN+ 0W20 will meet warranty requirements, but yes, if you're so inclined, you can run a D1G2 rated 0W20 or XW30 oil if you prefer. But there's not any real data to show that Subaru's recommendation is insufficient for the engine as it rolls off the factory floor. Sweet car BTW, let us know how you like it once it's broken in!
Subaru recommended 5W30 for the FA20DIT, at least when my FXT's owner's manual was printed, so I doubt there has been much experience with 0W20 in that engine.
We'd have to look at info for the Ascent to get any historical info about the 2.4l DIT with 0W20...and I doubt many owners of those are hanging around on NASIOC! ;^)
I get that the post I am replying to is referring to Subaru's general history with oil recommendations for its DIT engines, but, of course, a 0W20 recommendation for a turbo is going to raise heads on BITOG...especially when 5W30 was recommended for earlier DIT engines.
My wife bought a Legacy XT and seems pretty happy with it...she didn't choose the XT for its power, per se, but because it was much quieter than a similar Legacy with the 2.5l.
I was slightly surprised by the 0W20 recommendation given the DIT, but she is an extremely sedate driver and will not be stressing the engine very much....I also suspect that she will be having her car serviced by the dealer as I am an idiot who will surely destroy her vehicle.
I have only driven the Legacy XT once...I didn't try hard to make it launch and got the feeling that it would probably not be a strong point of that vehicle. I was VERY impressed by the passing power using the downshift paddle, though, that sucker just took off! I also had 93 octane in it at that point, sorta by accident as I am used to buying it for my FXT...but the car seems to run just fine on 87.