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2014 Legacy oil - SUbaru synthetic or Mobil one, or other?

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Exactly. 0w20 is for economy, emissions

 

As a one-size-fits all approach for your business you have to recommend stick with 0w20 for warranty purposes and then switch to 5w30 after?

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So far they haven't been able to mass produce a reliable engine to use the 0w16 spec or they would. That's how close to the edge they are running with 0w20. They can't yet build one for 0w16 and get it to hold together.

GD

We'll see if it's true or not. But I've heard from my oil distributor that select Honda and Toyota engines are going to come factory filled with 0w16 for this model year.

Not all of their engines. But like one or two.

Either way. If you filled a 0w16 engine with 0w20 is it actually going to matter?

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We'll see if it's true or not. But I've heard from my oil distributor that select Honda and Toyota engines are going to come factory filled with 0w16 for this model year.

Not all of their engines. But like one or two.

Either way. If you filled a 0w16 engine with 0w20 is it actually going to matter?

Purely theoretical les than semi- educated guess - higher viscosity -> higher oil pressure, and higher heat losses -> higher temps for the rubbing parts. OTOH - there are other factors to play here - heat transfer properties of the oil, etc... Only the real data would tell, Anybody has experience running this engine on 5w30 for ~100kmiles or more?. 

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As a one-size-fits all approach for your business you have to recommend stick with 0w20 for warranty purposes and then switch to 5w30 after?

Yes that's what we do. Once the 3/36 is up (assuming they don't have an extended) we switch to 5w30 XL. On the older stuff that tends to burn oil, or higher mileage stock turbo engines we run 5w40, and for all performance applications we run either 10w40 premium protection (high zinc) or 15w50 Dominator.

 

GD

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Anybody has experience running this engine on 5w30 for ~100kmiles or more?.

All the turbo models of the FB engine (15+ WRX) use 5w30. So yes there is certainly experience with it. Also the H6 engines like the 3.6R which are of similar design with respect to timing chains, clearances, dual AVCS, etc also come with the 5w30 recommendation. It protects better and is needed for the heavier loading of the higher performance engines.

 

If you want to protect your engine and insure against damage from high temperatures, bad gas, and hard driving - 0w20 just doesn't do that. And it's part of the reason for high oil consumption, and bearing failures being seen on the FB.

 

GD

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So if i could bring up a question here.

A lot of other Japanese car manufacturer use 5w20 in most of their cars for a long time. And now most of them switched to 0w20 for obvious reason.

 

But if they have successfully used 5w20 on their engine and most of them make it 200k+.

Are we talking there's an issue with subarus design that doesn't allow them to use thinner oils without compromising longevity.

 

Because the only real difference from 5w20 and 0w20 (assuming brand and quality of oil is the same) is the cold viscosity...

And while i realize cold starting and running until the engine reaches operating temperature is tough on the lubrication system etc.

 

Does the issue truly lie with the oil. Or subarus design not truly factoring in the 0w20 & longevity.

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Aluminium engine block has 2x the coefficient of thermal expansion compared to the forged iron crankshaft. This changes bearing clearances with respect to temperature on the mains, which feed the rods.

 

Subaru rod bearings are unusually narrow. Focusing the loads on a smaller bearing surface. This is because 5 main bearings, and 4 rod bearings are squished into the depth of less than 3 cylinders. Compared to an inline 4 cylinder design, the rod bearings are about 1/4" narrower. Just have a look at a conventional inline 4 crank next to the Subaru crank. The space for proper bearings of decent size doesn't exist.

 

The horizontal nature of the cylinders makes oil consumption a larger problem than with conventional inline or V engines which mostly have upright, naturally draining cylinders. This leads to engineering difficulties for thin oils, leading to consumption, and a higher incidence of running dry or running low enough to cause thermal damage to the oil by running it's volume through the engine at higher rate and not having sufficient surface contact with the pan, etc for cooling.

 

It's a troublesome design, and in many ways it's a terrible choice for performance. The Mitsubishi 4G63 put any Subaru 4 cylinder to shame by a very wide margin. Good thing Mitsubishi couldn't build a complete package with drivetrain, and electrics that weren't complete garbage or Subaru would have been in big, big trouble.

 

We work around it's shortcomings. But that does necessitate a very considered approach to lubrication. Its definitely one of the weak points on the Subaru engine and so requires special attention to oil film strength, bearing clearances, and oil pump volume.

 

GD

Edited by GeneralDisorder

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