Quickie: 0w20 vs 5w20 / 5w30

[bluesubie]

Originally Posted by garfull

what about 0W-30

Maybe a thin Resource Conserving 0W-30 with a low HTHS because it's not much thicker than a 0W-20, but definitely not a Euro 0W-30 like German Castrol which is almost a 40 grade.

With the good uoa's posted on this forum on 0W-20 I don't see a reason to use 0W-30 on a stock engine, unless you're tracking it (and not auto-x).

-Dennis

[SXE10]

Originally Posted by zoomzoomers

When I replaced the factory fill my motor took a solid 6 quarts of oil, which I though was a little strange since the manual lists 5.4 quarts (is it?).

It should only take 5.7qt or 5.4L in modern speak. You've probably over filled it. Engine dip sticks aren't always accurate

[zoomzoomers]

Originally Posted by SXE10

It should only take 5.7qt or 5.4L in modern speak. You've probably over filled it. Engine dip sticks aren't always accurate

I found it a little odd myself, but the techs said the same thing. That it took the entire 6 quarts.

[kuhlka]

Originally Posted by zoomzoomers

I found it a little odd myself, but the techs said the same thing. That it took the entire 6 quarts.

Were you using the stock filter? Some aftermarket filters are fatter or taller, which would possibly cover that extra 300ml. Most likely over-filling a bit.

[zoomzoomers]

Originally Posted by kuhlka

Were you using the stock filter? Some aftermarket filters are fatter or taller, which would possibly cover that extra 300ml. Most likely over-filling a bit.

I've used the OEM filer from Subaru the past two changes. It isn't the black one that came with the car, but the blue one that Subaru told me is the correct one for the car. I can't see that as an issue as I normally ask the techs to let the oil drain completely from the motor before filling it back up with new oil.

[504]

Just a few things to note;

* 90% of engine wear occurs at start-up/first 20 minutes of driving or so. Increasing to a 5W30 WILL lead to a much higher viscosity on start-ups. Oil viscosity versus temperature is an exponential curve and as it dips below 40 degrees, viscosity begins to rise very quickly. The difference between a 0w20 and a 5w30 becomes quite significant at 20 Degrees Celcius and under.

* oil pressure builds as RPMs increase. Thicker oil requires more pressure for the same amount of flow and if the cars oil pump reaches maximum pressure at say 4000 rpm with a 40wt oil, you will get no more flow and hence no more extra lubrication as you keep revving to redline. The same car with a 20wt oil may still be able to provide extra flow to the engine at redline because it requires less pressure to get it moving. (this would be my biggest concern in a car designed for 20wt oil!)

* Thinner oils flow better, there is less resistance and hence less power loss and a more responsive engine. The starter motor works for less time meaning the alternator has to work less to charge the battery which has discharged less.

Moving to thicker oils make even less sense when you look at the viscosity differences at operating temperatures, 2 Cst difference between a 20wt and a 30wt is nothing and as you go higher the difference gets less and less. If anyone was concerned with caring for their engine during high load situations, oil cooler with a 0W20 would be ideal.

[regal]

Originally Posted by 504

Just a few things to note;

* 90% of engine wear occurs at start-up/first 20 minutes of driving or so. Increasing to a 5W30 WILL lead to a much higher viscosity on start-ups. Oil viscosity versus temperature is an exponential curve and as it dips below 40 degrees, viscosity begins to rise very quickly. The difference between a 0w20 and a 5w30 becomes quite significant at 20 Degrees Celcius and under.

* oil pressure builds as RPMs increase. Thicker oil requires more pressure for the same amount of flow and if the cars oil pump reaches maximum pressure at say 4000 rpm with a 40wt oil, you will get no more flow and hence no more extra lubrication as you keep revving to redline. The same car with a 20wt oil may still be able to provide extra flow to the engine at redline because it requires less pressure to get it moving. (this would be my biggest concern in a car designed for 20wt oil!)

* Thinner oils flow better, there is less resistance and hence less power loss and a more responsive engine. The starter motor works for less time meaning the alternator has to work less to charge the battery which has discharged less.

Moving to thicker oils make even less sense when you look at the viscosity differences at operating temperatures, 2 Cst difference between a 20wt and a 30wt is nothing and as you go higher the difference gets less and less. If anyone was concerned with caring for their engine during high load situations, oil cooler with a 0W20 would be ideal.

Good argument but there is very very little history with any Subaru boxer running an oil which such a low HTHS. A lot of Subaru owners move up to Rotella and reported fewer spun rod bearings. Of course the FA20 is a new design. But the fact that the service manual posted above lists 5w-30 makes one wonder if the new engine deign is really optimal with the higher HTHS of a 30 weight. I wish I had the answer. A 0w-30 may smart.

Then again the latest ow20 sustina is the best UOA we have seen ( see thread below). It may be the previous success with Rotella in Subaru's was due to higher protection from ZDDP as Sustina is supposed to have advanced additives that go beyond what ZDDP does as far as protection. It interesting to note that the Sustina UOA is much better than any of the Motul 300V UOA's which are full of anti-wear protection.

I'm changing my oil to 5Qt Mazda 0w20 High Moly + 0.5Qt Mobil Racing 0w30. The Mobil boosts the ZDDP to about the level of Rotella. But after seeing the Sustina UOA I wish I had spent the extra $'s for the Sustina. Right now its the only proven oil shown to stop copper bearing wear.

Time will tell but given previous history with Subaru boxers oil choice is critical.

[bluesubie]

Originally Posted by regal

Good argument but there is very very little history with any Subaru boxer running an oil which such a low HTHS. A lot of Subaru owners move up to Rotella and reported fewer spun rod bearings. Of course the FA20 is a new design. But the fact that the service manual posted above lists 5w-30 makes one wonder if the new engine deign is really optimal with the higher HTHS of a 30 weight. I wish I had the answer. A 0w-30 may smart.

Then again the latest ow20 sustina is the best UOA we have seen ( see thread below). It may be the previous success with Rotella in Subaru's was due to higher protection from ZDDP as Sustina is supposed to have advanced additives that go beyond what ZDDP does as far as protection. It interesting to note that the Sustina UOA is much better than any of the Motul 300V UOA's which are full of anti-wear protection.

I'm changing my oil to 5Qt Mazda 0w20 High Moly + 0.5Qt Mobil Racing 0w30. The Mobil boosts the ZDDP to about the level of Rotella. But after seeing the Sustina UOA I wish I had spent the extra $'s for the Sustina. Right now its the only proven oil shown to stop copper bearing wear.

Time will tell but given previous history with Subaru boxers oil choice is critical.

Keep in mind that the history that we have on Subaru boxer oil choices, and the preference to run Rotella T6 5W-40, is in turbocharged Subaru's that have historically allowed 5W-40 and even 50 grades in severe conditions. You're talking about 2.5T's pumping out 265-305 hp and 244-290 lb ft of tq in stock trim. Post 2011, turbocharged Subaru's now all spec 5W-30 with xW-40 no longer being allowed except for replenishment (not that I agree with that for the reasons you already mentioned!).

Given that many GF5 5W-30's will shear to a 20 grade in a turbocharged Subaru (and possibly even a BRZ/FR-S), how much more bearing protection can one expect from an xW-30 anyway? 50 bucks says that n/a Subaru's will be back-specced to 0W-16 when the new GF6 spec comes out.

-Dennis

[regal]

Originally Posted by bluesubie

Keep in mind that the history that we have on Subaru boxer oil choices, and the preference to run Rotella T6 5W-40, is in turbocharged Subaru's that have historically allowed 5W-40 and even 50 grades in severe conditions. You're talking about 2.5T's pumping out 265-305 hp and 244-290 lb ft of tq in stock trim. Post 2011, turbocharged Subaru's now all spec 5W-30 with xW-40 no longer being allowed except for replenishment (not that I agree with that for the reasons you already mentioned!).

Given that many GF5 5W-30's will shear to a 20 grade in a turbocharged Subaru (and possibly even a BRZ/FR-S), how much more bearing protection can one expect from an xW-30 anyway? 50 bucks says that n/a Subaru's will be back-specced to 0W-16 when the new GF6 spec comes out.

-Dennis

A good 0w30 won't shear to 20w, I am chosing 0w20, my only concern is HTHS and rod bearings. Time will tell what's the right choice.

Best data we have right now is the UOA of 0w20 Sustina showing no copper bearing wear. Hope the less expensive 0w20's perform as well.

[Suberman]

Turbos cook their oil in the turbo bearings. There is no connection whatsoever between viscosity required for turbo engines as compared to viscosity for NA engines.

Also, viscosity has almost nothing to do with engine protection. ALWAYS use the oil recommended by the engine manufacturer.

Bearing clearances are maintained by rotational wedging of the oil film. Oil pressure is required to push oil through the bearings at the correct rate to maintain oil temperatures at the correct level. Using oil with the wrong viscosity can actually burn out your bearings if that flow rate is slowed up, just for example.

Modern engines use low viscosity oil primarily for fuel economy (power is better with less viscous oil) but that doesn't mean using higher viscosity will only reduce power and increase fuel consumption. It can also destroy your engine and void your warranty.

There's a lot of complete nonsense bandied around on bulletin boards like this one. Unless you are an engine or lubrication engineer expert in the design and operation of your Subaru engine then just use the oil Subaru tells you to use.

[WWFT86]

Check out this link from Subaru Japan's website. Some Google translate may be needed if you don't read Japanese
http://www.subaru.jp/accessory/engine_oil/engine_oil/

and out of all these options it seems this 0W-30 is the bet all-around (e.g. cold weather starts, high temperature engine protection, bumper to bumper stop and go traffic), and lists BRZ specifically listed as a suitable car:
http://www.subaru.jp/accessory/engin...miumoil01.html

[Ernest72]

Don't overthink it. I have 116k on my 04 WRX wagon. I have used The dreaded M1 5w30, then switched to T6 5w40 and now I run castrol euro 0w30 in the winter, T6 in the summer. No issues two beautiful oil reports at about 50 and 100k.

The BRZ gets Subaru 0w20 and not worried a bit. Get it from Amazon.

Both cars are DD and driven sprited but No tracking.

[Overdrive]

Originally Posted by garfull

what about 0W-30

I am glad I found this so I wouldn't be the first one stating it. Why not just go with a 0W-30? There seems to be this unjustified fear of running a 0W oil in today's cars. People are focusing on the wrong number.

0W (W being Winter, not Weight) is the important part for cold weather. If you want something a bit thicker at running temp, 0W-30 will do that at the cost of some fuel economy and power that you won't terribly notice since you're not wringing the car out every second of your commuting. But at least at startup you'll be better protected with some more oil flow versus a 5W-anything. That's where the W number really matters.

[Somerandom18]

Just go with https://www.cermastore.com/evo-synthetic-motor-oil.html and never worry about it again.

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