Oil Recommendation :2020 Subaru Legacy 2.4 turbo

My dealer service advisor said they haven't had any issues with Ascent's running 0W-20. Yet. grin2 The operational viscosity of a GF 5W-30 (as used in the 2.0 DIT's) is not really that much thicker than the operational viscosity of a 20 grade (that's used in a 2.4DIT) after some shearing and/or fuel dilution. I'm tempted to go with a 5W-20 next for lower Noack and less VII's. Back to the OP's question. Brand doesn't really matter. Specs matter most. drive
 
Subaru OEM oil filter is fine, Wix/Napa Gold as well as Fram Ultra and Tough Guard filters work just as well too. In my Subarus I prefer to use Valvoline Advanced Synthetic but I have been using Shell Rotella Gas Truck and Pennzoil Platinum recently with their deals to be had.
 
What we don't know, is how much different the FA24DIT is from the FA20DIT. On paper, the 24 is simply a bored-out 20. I've thought about this for a little while and, while I'm no expert on either engine, I'd be curious about the following before I could give a really adequate answer: 1. Bearings: IF all of the internal bearings are the same I'd be apprehensive using XW-20. -----HOWEVER, we know that Subaru's 5W-30 syn shears to a 20wt quickly, so there are likely a good portion of FXT and WRX owners effectively running around with a 20wt anyway... 2. Octane: We know that the FA20DIT was tuned from the factory to utilize 93 AKI fuel. The FA24DIT was tuned for 87 AKI and won't benefit from higher octane w/ out an aftermarket tune. It has to be true that this engine can run regular fuel in large part due to the ECM's fueling scheme. I'd like to know whether this results in a substantial increase in fuel dilution for those who like to stay in boost often. 3. Power output between the two engines is very close (not that PEAK numbers really tell the whole story): -----HP is only 4% higher and Tq is only 7% higher with the FA24DIT, which -----I'm not saying a 20% increase in displacement will result in an equivalent increase in output, just that it doesn't appear that Subaru is really pushing this engine to the limit. Conclusions: 1. Subaru seems to like to play things relatively safe and, based on the FA20DIT being around for so long leads me to believe that they've had plenty of time to carry over any lessons learned and improve on any design deficiencies to make the FA20DIT a pretty robust offering. I think it's safe to say that following the owner's manual will VERY likely result in many years of good service 2. WITH ALL OF THAT SAID: I was a guinea pig for Subaru when I purchased my FA20DIT-powered '14 Forester XT. Many of us, myself included, experienced a ton of teething issues that resulted in inspections and half a dozen ECM flashes to resolve the many issues. Because of this, I would never buy a vehicle with an engine less than a few years old from Subaru again. While everything is running smoothly now, it took years to get things settled, so regardless of EVERYTHING I typed above, I'd be wary of this new engine...for now. The engine has been in the Ascent for a couple of years, has spread to two other models (if you count the Legacy and Outback as different enough to warrant comparison, based on their history on the same platform and now that everything is on the Subaru Global Platform (SGP), and will likely spread further (can we all say together, "400HP/Tq STI, please, Subaru!!!"?
 
Originally Posted by gathermewool
2. Octane: We know that the FA20DIT was tuned from the factory to utilize 93 AKI fuel. The FA24DIT was tuned for 87 AKI and won't benefit from higher octane w/ out an aftermarket tune. It has to be true that this engine can run regular fuel in large part due to the ECM's fueling scheme. I'd like to know whether this results in a substantial increase in fuel dilution for those who like to stay in boost often.
When working on the AccessPort for the Ascent, Cobb stated (either on Facebook or the Ascent forum), that they experienced light knock events with 87.Although they didn't go into too much detail. The owner's manual says:
Quote
Using a gasoline with a lower octane rating can cause persistent and heavy knocking, which can damage the engine. Do not be concerned if your vehicle sometimes knocks lightly when you drive up a hill or when you accelerate. See your dealer or a qualified service technician if you use a fuel with the specified octane rating and your vehicle knocks heavily or persistently.
Then there's fuel dilution. I've seen people complaining on the Outback forum that they can only do two consecutive remote starts at 10 minutes each via the Starlink app. Of course, these same people will probably complain that they smell fuel in the oil.
 
My $0.02..... I'd never run 87 octane in a turbocharged car I don't care what it is or how it's tuned from the factory. End of story. If you want to stick to the 0w-20 recommended, I'd suggest look into Motul ecolite 0w-20. I use Motul in many Subaru's I work on and it's been stellar in all of them.
 
Originally Posted by bluesubie
Originally Posted by gathermewool
2. Octane: We know that the FA20DIT was tuned from the factory to utilize 93 AKI fuel. The FA24DIT was tuned for 87 AKI and won't benefit from higher octane w/ out an aftermarket tune. It has to be true that this engine can run regular fuel in large part due to the ECM's fueling scheme. I'd like to know whether this results in a substantial increase in fuel dilution for those who like to stay in boost often.
When working on the AccessPort for the Ascent, Cobb stated (either on Facebook or the Ascent forum), that they experienced light knock events with 87.Although they didn't go into too much detail. The owner's manual says:
Quote
Using a gasoline with a lower octane rating can cause persistent and heavy knocking, which can damage the engine. Do not be concerned if your vehicle sometimes knocks lightly when you drive up a hill or when you accelerate. See your dealer or a qualified service technician if you use a fuel with the specified octane rating and your vehicle knocks heavily or persistently.
Then there's fuel dilution. I've seen people complaining on the Outback forum that they can only do two consecutive remote starts at 10 minutes each via the Starlink app. Of course, these same people will probably complain that they smell fuel in the oil.
I remember reading something about that on one of the other Subie forums (maybe NASIOC, SF.org or LGT.com, etc.) but don't remember the details. FWIW, I still experience some light (what used to be called phantom in my EJ257-powered '08 STI) knock in my FXT on a Cobb Stage 1 93 map using 93 AKI fuel. I switched to the 91 map with 93 AKI fuel and still had pretty much the same amount of light knock. I'm guessing that the newest Subies have very sensitive knock sensors compared to a decade ago. Practically speaking, if the ECM is only picking up on light knock with the latest FA24DIT, then that provides even more reason NOT to run anything higher than 87 AKI fuel. Again, I'd have to do some more research, including refreshing my memory on what Cobb found, before deciding whether to run anything higher than 87 AKI fuel before doing so in my hypothetical FA24DIT-powered Subie. I will NOT run anything less than 93 AKi fuel in my FA20DIT-powered FXT, however, nor should anyone else out there. // I'm not sure what you're getting at re: max 2 remote-starts. Are you saying that Subaru programmed this in to mitigate excessive fuel dilution? What are other manufacturers doing re: how long auto-start duration and number of runs are concerned? I would imagine that the gov would get involved in something like this to minimize useless idling time and to minimize emissions and fuel consumption.
 
Originally Posted by STIcandy
My $0.02..... I'd never run 87 octane in a turbocharged car I don't care what it is or how it's tuned from the factory. End of story.
Not even if a reputable tuner or tuning company proved that the engine was indeed programmed to only run 87 AKI fuel?
 
Originally Posted by gathermewool
Originally Posted by STIcandy
My $0.02..... I'd never run 87 octane in a turbocharged car I don't care what it is or how it's tuned from the factory. End of story.
Not even if a reputable tuner or tuning company proved that the engine was indeed programmed to only run 87 AKI fuel?
We can't run 89 or 93 octane? For sure I wouldn't buy anything with that engine. Wait - One step further please! I'd never buy any turbocharged engine vehicle either.
 
Last edited:
Originally Posted by Triple_Se7en
Originally Posted by gathermewool
Originally Posted by STIcandy
My $0.02..... I'd never run 87 octane in a turbocharged car I don't care what it is or how it's tuned from the factory. End of story.
Not even if a reputable tuner or tuning company proved that the engine was indeed programmed to only run 87 AKI fuel?
We can't run 89 or 93 octane? For sure I wouldn't buy anything with that engine. Wait - One step further please! I'd never buy any turbocharged engine vehicle either.
Of course you can, you just won't benefit from higher octane rating, it will only be a waste of money. As for turbo engines, at some point almost all ICE engines will be turbocharged for fuel efficiency.
 
Originally Posted by gathermewool
I'm not sure what you're getting at re: max 2 remote-starts. Are you saying that Subaru programmed this in to mitigate excessive fuel dilution? What are other manufacturers doing re: how long auto-start duration and number of runs are concerned? I would imagine that the gov would get involved in something like this to minimize useless idling time and to minimize emissions and fuel consumption.
Warming up a cold car before driving. Subaru's of the past few model years have the ability to start remotely via the Starlink app. Subaru limits this by shutting the car off after the first 10 minutes and allowing only one remote restart and it shuts off again in 10 minutes. People in extreme cold want to let it warm up for longer than 20 minutes. oilburner
 
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Originally Posted by Triple_Se7en
I never had a vehicle (since 1969) that didn't seem to run better, when switching from 87 to 93 octane.
If your car isn't tuned to take advantage of a higher anti knock index it will not change how the car runs in any way. Higher octane does not produce more energy, it is simply more resistant to detonation which is useful in high compression and turbo engines. The engine in question in this post has most likely been detuned to be able to use 87 octane. But with a proper tune, it would make more power with a more stable fuel (91 or 93 octane.)
 
Originally Posted by jbutch
Originally Posted by Triple_Se7en
I never had a vehicle (since 1969) that didn't seem to run better, when switching from 87 to 93 octane.
If your car isn't tuned to take advantage of a higher anti knock index it will not change how the car runs in any way. Higher octane does not produce more energy, it is simply more resistant to detonation which is useful in high compression and turbo engines. The engine in question in this post has most likely been detuned to be able to use 87 octane. But with a proper tune, it would make more power with a more stable fuel (91 or 93 octane.)
That is not entirely true. Many ECM's are set up with a high and low octane ignition timing tables from the factory. When the engine detects knock, it will revert to the low octane timing tables to protect the engine from detonation and damage. In said ECM it will always try the advanced ignition table when the car is started and will retard quickly if it finds knock indicating it is running regular fuel. You are correct in saying there is not more energy in higher octane fuel, there is more resistance to knock, this allows for higher compression ratios, advanced ignition timing, higher boost thresholds and often times better fuel economy because you aren't trying to "quench" the detonation via fuel enrichment (think Honda's current turbo engines and their fuel dilution issues) Today's engines may not always have both timing tables. I'd surmise that most NA applications (especially the small displacement engines) probably don't. I would tend to believe that most if not all turbocharged cars would have these parameters built in and would benefit from premium fuel. I bet money most of the HP ratings touted by the manufacturers are not run on 87 octane fuel.
 
Originally Posted by jbutch
Originally Posted by Triple_Se7en
I never had a vehicle (since 1969) that didn't seem to run better, when switching from 87 to 93 octane.
If your car isn't tuned to take advantage of a higher anti knock index it will not change how the car runs in any way. Higher octane does not produce more energy, it is simply more resistant to detonation which is useful in high compression and turbo engines. The engine in question in this post has most likely been detuned to be able to use 87 octane. But with a proper tune, it would make more power with a more stable fuel (91 or 93 octane.)
You are absolutely correct. My Hyundai fares no better with 93 Octane. I just wanted to confirm this with someone else. I couldn;t believe it at first. Thought I was just imagining the vehicle's 2.4GDI not running any better on 93. Well I guess there's a first time for everything..... even engine performance changes never encountered before. Thanks.
 
My wife's Hyundai 2.0T runs no better on 93 than on 87. Even though I fill it up mostly with 93, my better (smarter) half uses 87 and I can never tell by feel, sounds or mpg. I'm now running 87-89 in the Passat 2.0T Budack Cycle. Same thing, no difference whatsoever.
 
Originally Posted by wemay
My wife's Hyundai 2.0T runs no better on 93 than on 87. Even though I fill it up mostly with 93, my better (smarter) half uses 87 and I can never tell by feel, sounds or mpg. I'm now running 87-89 in the Passat 2.0T Budack Cycle. Same thing, no difference whatsoever.
What does the manual specifies for fuel? If it's 87, than it means it's most likely tuned for 87 and won't gain much (or not at all) by putting 93.
 
I just picked up a case of the new Pennzoil 0w-30 MAX POWER!!! Also submitted for the current $25 rebate grin2 I bought it to use in my Hyundai GDI but may end up using it in my Subaru (that calls for 0w-20) instead. If these engines are prone to shearing a 30w oil down to a 20w why not just go with a 30w to begin with?
 
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