Condor1970 Posted October 19, 2019 Share Posted October 19, 2019 I have always been a little concerned with running such thin oil (0w20) in my wife's 2017 2.5L Legacy, and noticed something while perusing the official Subaru parts website. I looked up her car, and they also list 5w30 full synthetic as an available oil in 5qt jugs. Is this a potential problem if I switch? I have always seen 5w30 full syn as a more protective oil, even though the gas mileage may go down slightly. After spending a lot of money for a brand new car, I would rather have my engine last than use oil as thin as water to max out my gas mileage. Has anyone made the switch? Are there any potential issues I should be worried about? Link to comment Share on other sites More sharing options...
ammcinnis Posted October 19, 2019 Share Posted October 19, 2019 (edited) The "thicker is better" myth is both intuitive and wrong. Clearances in the FB25 engine are engineered for 0W-20 oil, and it is the oil viscosity specified in both the Owners Manual and Factory Service Manual. That said, it is unlikely that even long-term use of a 5W-30 oil is going to hurt anything. On the other hand, the EZ36 engine (a decade-older design) was engineered to use 5W-30 oil, which probably explains the listing you found. Edited October 19, 2019 by ammcinnis "If you don't know where you're going, any road will take you there." ~ The Cheshire Cat (Alice in Wonderland) Link to comment Share on other sites More sharing options...
Condor1970 Posted October 27, 2019 Author Share Posted October 27, 2019 From what I know, all the main clearances in the 3.6 and the 2.5 are the same. 0w20 is engineered to maximize HP and efficiency, not necessarily protection. So, if that's the case, why would it be a problem running 5w30? Link to comment Share on other sites More sharing options...
ammcinnis Posted October 28, 2019 Share Posted October 28, 2019 Your car, your choice. It sounds like you have already decided. "If you don't know where you're going, any road will take you there." ~ The Cheshire Cat (Alice in Wonderland) Link to comment Share on other sites More sharing options...
tmoney468 Posted October 29, 2019 Share Posted October 29, 2019 The manual calls for 0w-20, why would you use anything other than that? People have tried different weights to see if it helped oil consumption (which it never really did). Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
whitetiger Posted October 29, 2019 Share Posted October 29, 2019 (edited) the only time to think about switching to a heaver weight is when you achieve high mileage and notices some consumption between OCIs. otherwise, run the weight the manual calls for. period. Edited October 29, 2019 by whitetiger Link to comment Share on other sites More sharing options...
balbrec2 Posted October 29, 2019 Share Posted October 29, 2019 From what I know, all the main clearances in the 3.6 and the 2.5 are the same. 0w20 is engineered to maximize HP and efficiency, not necessarily protection. So, if that's the case, why would it be a problem running 5w30? From what I know, the design engineers at Subaru are a lot smarter than you or I. Stick with what they recommend. Link to comment Share on other sites More sharing options...
YeuEmMaiMai Posted October 30, 2019 Share Posted October 30, 2019 i dunno if you live somewhere where it gets hot, a slightly thicker oil may be desireable... have you seen 0w20 oil come out of any engine that has been worked hard? can you say consistency of water? From what I know, the design engineers at Subaru are a lot smarter than you or I. Stick with what they recommend. from what we know, maybe not, FB series have a few weaknesses that are not present in previous engines... valve springs and con rods come to mind Link to comment Share on other sites More sharing options...
Oldpilot Posted January 2, 2020 Share Posted January 2, 2020 Subaru wants the highest mileage figure possible, and they know the engine won't die within the warranty period. They don't care what happens six or eight years down the line. Link to comment Share on other sites More sharing options...
WILLINH Posted January 2, 2020 Share Posted January 2, 2020 I stay with 0-20 BUT I change it at 5,000 or a hair over. Never have gone to 6,000. I now have 80,000 on my 16 and it does not use oil. Link to comment Share on other sites More sharing options...
Brisvegas Posted January 3, 2020 Share Posted January 3, 2020 I have always been a little concerned with running such thin oil (0w20) in my wife's 2017 2.5L Legacy, and noticed something while perusing the official Subaru parts website. I looked up her car, and they also list 5w30 full synthetic as an available oil in 5qt jugs. Is this a potential problem if I switch? I have always seen 5w30 full syn as a more protective oil, even though the gas mileage may go down slightly. After spending a lot of money for a brand new car, I would rather have my engine last than use oil as thin as water to max out my gas mileage. Has anyone made the switch? Are there any potential issues I should be worried about? Maybe this link might interest you ... https://blog.amsoil.com/what-happens-if-i-use-the-wrong-weight-viscosity-of-oil/ Link to comment Share on other sites More sharing options...
WILLINH Posted January 3, 2020 Share Posted January 3, 2020 (edited) For what it's worth, My 2019 5.7 Tundra uses 0-20 oil. I am not concerned at all about the weight of the oil. Edited January 3, 2020 by WILLINH Link to comment Share on other sites More sharing options...
ammcinnis Posted January 3, 2020 Share Posted January 3, 2020 Subaru wants the highest mileage figure possible, and they know the engine won't die within the warranty period. They don't care what happens six or eight years down the line. And you know all this ... how? "If you don't know where you're going, any road will take you there." ~ The Cheshire Cat (Alice in Wonderland) Link to comment Share on other sites More sharing options...
Brisvegas Posted January 3, 2020 Share Posted January 3, 2020 Subaru wants the highest mileage figure possible, and they know the engine won't die within the warranty period. They don't care what happens six or eight years down the line. I agree with your first statement ... because Subaru, like all manufacturers, obviously want to achieve the highest mileage figure they can ..... but your last sentence is pretty silly in my opinion. If Subaru designed their vehicles to only last six or eight years, how many people in the future would be buying their vehicles? Longevity and reliability has been one of the mainstays of Subaru sales over the years ... and whilst some might question some of the decisions that the Subaru boardroom boffins make at times ... surely designing cars to only last 6 or eight years would not be one of them. Link to comment Share on other sites More sharing options...
waldguy Posted January 4, 2020 Share Posted January 4, 2020 I'm not sure why people go looking for a better solution to the manufacturers recommendations. The engineers who designed the engine build it with the oil characteristics in mind. They know a heck of a lot more about the flow and the lubrication qualities needed within the tolerances they've specified. I'll default to the MFR recommendations over forum banter 100 out of 100 times. Link to comment Share on other sites More sharing options...
aki334 Posted January 6, 2020 Share Posted January 6, 2020 (edited) the only time to think about switching to a heaver weight is when you achieve high mileage and notices some consumption between OCIs. otherwise, run the weight the manual calls for. period. I agree with the above. You might be ok with 5w 30 if you are in extreme hot temperatures and are using car as uber driver or taxi, anything else go with 0-20 from Walmart Edited January 6, 2020 by aki334 Link to comment Share on other sites More sharing options...
Condor1970 Posted January 30, 2020 Author Share Posted January 30, 2020 (edited) UPDATE: I just got done talking with my local dealer parts department, and also the mechanics. They said that 5w30 Synthetic Oil is actually an alternate for the 2.5L engine. It is also listed on the Subaru Website for parts and oil recommendations right below the listing for 0w20. This is what they ran in all the 2.5L engines in prior years, and changes in clearance are not an issue. In fact, they run 5w30 in all the turbo engines they service at the dealer. It provides more protection with a slightly stronger film at higher temps, and also helps protect against oil consumption by preventing premature wear from the thinner 0w20 oil that does not have as high an impact pressure rating rating as 5w30. He even said the only main reason they went to 0w20 oil in the 6th Gen, is to help meet CAFE standards for fuel efficiency, and if you don't mind getting maybe 0.5-1.0mpg less, then 5w30 full synthetic is perfectly fine. That 0w20 is like water, and no wonder they are having oil consumption problems in the new gen engines. I think I'm going to make the switch before it becomes a problem for me. Edited January 30, 2020 by Condor1970 Link to comment Share on other sites More sharing options...
YeuEmMaiMai Posted February 1, 2020 Share Posted February 1, 2020 ^5th gen 13+ cars with 2.5L also use 0w20... Link to comment Share on other sites More sharing options...
tmoney468 Posted February 1, 2020 Share Posted February 1, 2020 If you read the manual, it says you can use 5w-30 if you have to, but to change back to 0w-20 as soon as possible. Still no clue what the point of this is. They designed the engines to use 0w-20. The majority of the oil consumption were due to the tolerances in their short block ring designs. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
ammcinnis Posted February 1, 2020 Share Posted February 1, 2020 (edited) Still no clue what the point of this is. They designed the engines to use 0w-20. IMO, this is the result of two major factors: Relentless advertising, over more than a century, both by the oil companies themselves and by aftermarket oil additive vendors.The conceit of many car owners that they know more than the engineers who designed the engines and the lubricants used in them. Chief among these conceits is the tenacious myth that "thicker is better." Edited February 1, 2020 by ammcinnis "If you don't know where you're going, any road will take you there." ~ The Cheshire Cat (Alice in Wonderland) Link to comment Share on other sites More sharing options...
waldguy Posted February 3, 2020 Share Posted February 3, 2020 .... Chief among these conceits is the tenacious myth that "thicker is better." Well put. Pretty much every oil is "thin" at operating temperature. During the cool down, the hot "thicker" oil is not going to leave a film on the metal parts any more than than the thinner oil. The phase where wear is at greatest risk is start-up and warm-up. That's the time the thinner oil is most desirable -- it flows freely when cool and gets those moving parts lubricated. 5w30 will probably be acceptable for longer term use, but 0w20 is likely to protect better. I wouldn't listen to the logic of a local dealer on this one. When I picked up my new car, the dealer was adamant that my engine took 6 liters. I told him the car takes 5 (I read the manual before I picked up the car). He said that was the previous generation. I disagreed, but bought one extra liter for a spare. I haven't used a spare liter in 5 years. Link to comment Share on other sites More sharing options...
hallowground Posted February 4, 2020 Share Posted February 4, 2020 So take for example the 3.6 engine. When it first came out it said the oil change interval was 7500 miles or 3750 in severe environment. Now it is 6000 or 3000 in severe. What changed to the engine? Not a single thing. I think they realized they were having consumption issues and customers were noticing by going 7500 miles so they reduced the interval. However if the 2.5L engine is the same ej as it was 5 years ago it should be fine taking the old type of oil. Most companies are putting the thin oil from factory because of gas mileage which is stupid. The cost to fix an engine when it wears out or replace the consumed oil outweighs the cost of fuel. Btw burning oil is not great for emissions. Personally I would use 5w30 on all the subaru engines that say it can be used. I would also use premium gas too on all subarus but that is a completely different subject. Their compression ratio is too high to be running on 87 octane... there is a reason why subarus develop engine knock so early and it is mainly because of using lower octane of a long period of time. Sent from my SM-G935V using Tapatalk Link to comment Share on other sites More sharing options...
ammcinnis Posted February 4, 2020 Share Posted February 4, 2020 ... there is a reason why subarus develop engine knock so early ... You state that as if it were an established fact. It is not. "If you don't know where you're going, any road will take you there." ~ The Cheshire Cat (Alice in Wonderland) Link to comment Share on other sites More sharing options...
YeuEmMaiMai Posted February 4, 2020 Share Posted February 4, 2020 So take for example the 3.6 engine. When it first came out it said the oil change interval was 7500 miles or 3750 in severe environment. Now it is 6000 or 3000 in severe. What changed to the engine? Not a single thing. I think they realized they were having consumption issues and customers were noticing by going 7500 miles so they reduced the interval. However if the 2.5L engine is the same ej as it was 5 years ago it should be fine taking the old type of oil. Most companies are putting the thin oil from factory because of gas mileage which is stupid. The cost to fix an engine when it wears out or replace the consumed oil outweighs the cost of fuel. Btw burning oil is not great for emissions. Personally I would use 5w30 on all the subaru engines that say it can be used. I would also use premium gas too on all subarus but that is a completely different subject. Their compression ratio is too high to be running on 87 octane... there is a reason why subarus develop engine knock so early and it is mainly because of using lower octane of a long period of time. Sent from my SM-G935V using Tapatalk the legacy has had the FB25 since 2013 model year and it has required 0W20. The Forrester has had the FB25 since 2010 and also requires 0W20. and what do you mean their compression ratio is too high? 10.x is the new normal now for naturally asperated SMPFI engine 2003 Legacy with 142K, 2010 Outback 3.6R, and 2014 Legacy 2.5I ALL run just fine on 87. All 3 engines have knock control... given the power levels that other have with 2.5L, I would suggest Subaru are tuned for fuel consumption vs power... honda and Toyota have 3.5L that are well into the 270hp range...vs 256 for the Subaru... Link to comment Share on other sites More sharing options...
NORULZleggy Posted February 20, 2020 Share Posted February 20, 2020 I noticed my 2013 FB25 was eating some oil, I run Amsoil in all my cars, and was running 0W-20. I had some Amsoil 5W-30 sitting around from my old WRX and put it in and had no issue. I went back to 5W-20 and will be changing my oil this weekend. I have know the 0w-20 was for miles and blah blah for a while. these car a tuff. I also did a deep dive and only on paper can you tell a difference between oil when it comes to 0w-20 - 5W20, and 5w-30 - 10W-30. Link to comment Share on other sites More sharing options...
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