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2009 xt
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8 Posts
Discussion Starter · #1 ·
Hello everyone,

The previous owner of my vehicle has replaced a new engine,
Since the vehicle traveled about 10 thousand kilometers.

The car serves me everyday for my business and most of the trip is in traffic jams,

40 minutes in each direction

It's only at the end of the week that I travel faster but during the week my trip is calm

It is important to note that the country where I live is hot, in the summer temperatures can reach 40 degrees (Israel)

Should I switch to 5W40 oil?
Or use 10 W60 again

Thanks.
 

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2009 xt
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8 Posts
Discussion Starter · #3 ·
I would appreciate a more detailed explanation

The question is why it is better for me to switch to 5 W40
 

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2017 Forester XT Touring
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314 Posts
I do not understand why?

Lots of people use this oil ON STI...
oil has a film that it leaves behind the thickness of this film and its ability to penetrate engine compnents vary based on the viscosity. the car was built for a 30 weight oil, so you can usually fudge slightly lighter or slightly heavier, but going to 10w60 is a really big change and is likely to result in accelerated wear within your motor due to lack of sufficient lubrication. I'd stick to 5w40 as well and if you are concerned, change the oil more often, but i'd probably suggest doing an oil analysis before assuming you need it.
 

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MY05 Forester 2.5 XT 5MT
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3,078 Posts
There is likely a reason why the previous owner used 10W60 oil. If you have no problems, I would continue using it

I have a rebuilt engine and run 10W50 oil as was recommended to me. And no, it will not kill your bearings or any other bull someone dreams up in their fairy land

It is sad it has to be stated but: BMW engines are not Subaru engines.
 

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2006 Forester XTE 5 speed manual
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284 Posts
Whilst it is likely there is a reason why the previous owner used 10w60, it may simply be because he was misguided.

Call me old fashioned, but the engine is designed to run at the same water and oil temperatures, regardless of outside air temperature. Sticking in a thicker oil will simply inhibit the oil flow and potentially damage the bearings. If you want to test the theory - take the thermostat out of your engine and see how long the big ends/mains last....

We all keep our revs down until the engine is warmed up (I hope). Using a thicker oil will have similar effects to a cold engine.

Yes, BMWs are nothing like Subarus. Almost as different as 5w40 is to 10w60.
 

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2018 X3 M40i / 2016 X3 xDrive35i
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1,632 Posts
There is likely a reason why the previous owner used 10W60 oil. If you have no problems, I would continue using it

I have a rebuilt engine and run 10W50 oil as was recommended to me. And no, it will not kill your bearings or any other bull someone dreams up in their fairy land

It is sad it has to be stated but: BMW engines are not Subaru engines.
I am unclear on how much you understand about clearances but oil specifications are closely matched to clearances. Higher clearances will allow for cooler temps under higher speeds and pressures but require greater film strength in a higher viscosity oil. This is fine, IF you have higher clearances designed for that. If you don't you're going to be dealing with problems with cold flow lubrication and increased wear, and then an issue with higher friction levels with increased heat on those bearings.

BMW engines are not Subaru engines, you're right. But we're talking about engineering and that's universal. BMW is one of the few OEMs that opted to use 10w60 for a time.

This isn't fairy land, this is engineering. The unfortunate thing is that people don't know what they are doing and because there's not an immediate failure, they think everything is just fine. The M's were having bearing failures at various mileage but it seemed like 60-80k was about when you'd expect to replace them. It wasn't immediate, it took time.

If the person who built your engine recommended 10w50, use it and hope they spec'd properly for it. Taking that advice from anyone other than your engine builder is at your own risk, and probably unwise. But even at that I'd feel a lot more comfortable running 10w50 than 10w60.
 

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2012 Forester XT AT
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92 Posts
There is likely a reason why the previous owner used 10W60 oil. If you have no problems, I would continue using it

I have a rebuilt engine and run 10W50 oil as was recommended to me. And no, it will not kill your bearings or any other bull someone dreams up in their fairy land

It is sad it has to be stated but: BMW engines are not Subaru engines.

Just cause the last owner or a mechanic used something or did something doesn't mean it's right e.g. that idiot Scotty Kilmer on youtube has over 280,000 people watch him instructing people to put dielectric grease on the metal part of the spark plugs and in the connectors of wires! There's guys on here telling people to run their engines for a few min to cool the turbo or get a turbo timer.

Look, the engine is designed for 5W-30 weight, and they factor in a bunch of things that's beyond my current understanding...In his area, avg temperature year round is 6*C to 40*C. Once your engine is at optimal running temperature the coolant will keep it at that temperature range and that's at around 94*C (way hotter than the hottest recorded temperature on earth).

Yes, outside temperature can affect your engine when its starting up. That's when the oil is in the pan so having the correct W grade will help lube the engine when its cold. But when the engine is warmed up, the outside temperature shouldn't matter because the engine operating temperature is beyond the outside temperature of around 94*C. What the outside temperature does have an effect on is the cooling system. Your higher grade oil isn't going to cool your engine any better than the lower grade one and if your engine is running hot that it overcomes the cooling system because of the outside temperature, oil viscosity is the last of your problem. Your gasket can blow sending coolant to place it should be because of the different rate of contraction/expansion of the different metal, the cylinder can warp, and other component can fails.

Engine oil is mainly for metal on metal protection and some engine generate more heat or more stress and require higher grade. Subaru took this into consideration and designed other components to work with 5w30. I would probably would just upgrade to high performance/racing radiator for better cooling and if you have a turbo, maybe a high performance intercooler too or just stop and let your engine cool down. strictly putting 60 grade oil cause its 40*C doesn't do any good. I live in southern california and our summer in certain places is about the same as Israel's summers. Stop thinking the middle east is the hottest place on earth, it just get less rainfall and that's all (they get more than los angeles). I've taken my FXT to death valley during the summer many times where its over 120*F with the AC on. You'll be fine buddy and if you don't believe me or anyone else, you gotta do your own research.
 

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2008 forester XT 4EAT
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184 Posts
As I already said I live In Israel too and I own 2008 sg9 fxt, I put mishi rad and also auto trans cooler and engine oil cooler I use motul 5w40 oil and it's just more than ok.
In the past I used to have Honda civic that I put turbo on it, and used motul 15w50 and I still think that the oil is what wrecked my engine.
And I put this oil only cause the mechanic told me so and why is that...? maybe he had the most money profit of it, may be it comes from lacking knowledge who knows.
So i learned to check...what's good the rest of the world good for me too.

Sent from...somewhere
 

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Doesnt the manual state you can go as thick as a 50 weight for the MY04-MY08?? Im assuming thats under certain circumstances. Does anyone know of a situation where a 10w50 or any 50 weight is used? Very high milage? What is recommended for lets say 200k mile ej25? Would you still recommend 5w30 in these cases? Or does anyone use a 50 weight oil?
 

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2012 XT Touring 4EAT
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3,751 Posts
<snip>Should I switch to 5W40 oil?
Or use 10 W60 again
10W60 or 5W40 for my XT 2009?
How about neither of the above?

I looked through this thread but could not find an obvious answer: Why not simply follow the manufacturer's recommendation (which is probably 5w30)? Are you experiencing some kind of problem with 5w30? If it ain't broke, don't fix it ;-)

That said, when using 5w30 you might monitor your oil usage very carefully. How much oil are you really using? If 1 quart per oil change, consider yourself lucky. If you are using more oil - using more than you prefer - then consider the following. When a vehicle is using oil, the easiest and cheapest solution is . . . simply add more oil.

You might also experiment with oil brands - Castrol Syntech might hold up a bit better than, say, Mobil-1.

You might also try a 0w30 rather than 5w30. If that sound counter intuitive, the reason it matters is this. Synthetic oils consist of a base stock plus additives and viscosity index modifies. Even within a single brand of oil (say Mobil-1), the base stock for 0w30 is probably different than the base stock for 5w30 . . . different as in 'better' or 'more robust'.

You might also experiment with the oil change interval. In North America, it's still 3,000 miles. From my experience with Mobil-1, there is little or no usage in the first 1000 miles; a bit more in the second 1000 miles and most of the usage occurs in the last 1000 miles. Watch this carefully. It's pretty clear to me that Mobil-1 starts out great, but starts degenerating as the oil change interval progresses.

You might add an air/oil separator. You are assuming that the oil is passing the rings, but it might be escaping through the PCV valve or breather.

Finally, if you're really adventuresome, you might try an oil additive like boron or MoS2. On my present 2012 FXT with 103k miles and a Grimmspeed AOS, I'm using Mobil-1 5w30 with MoS2 added. I can go 5000 miles and not use any oil - zero, nada, zip. I was able to do this same thing on an 2006 FXT which had 160k miles when I sold it - zero oil usage. Aside from bragging rights, the zero oil usage and extended OCI more than paid for the MoS2. I could extend the OCI beyond 5000 miles, but at some point the small oil filter would need changing.

p.s. Personally, I would avoid using a heavier oil unless you have exhausted all other options. As @Scooby24 stated 'Tolerances were not designed for a 60 weight oil.' IMHO, the tolerances were not designed for 50 weight either - maybe 40 weight as well. Heavier oils will make your engine less efficient and reduce cold start lubrication. There are several better options available.

The 2006 . . .



and the '12

 

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2019 Crosstrek 2018 Forester XT
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Actually 60wt oil will not damage the engine. 60wt oil is 24 cSts. @ 100C (operating temp). That is the viscosity that a 30wt. is at 155F. Your vehicle will run (with 30 wt at 155F all day long).

Does it make sense? No
 

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Actually 60wt oil will not damage the engine. 60wt oil is 24 cSts. @ 100C (operating temp). That is the viscosity that a 30wt. is at 155F. Your vehicle will run (with 30 wt at 155F all day long). Does it make sense? No
Does it make sense? No. If you're going to compare oil weights, why not compare 30wt oil at 100C to 60wt oil at 100C? There's enough confusion and misinformation in this area without adding to the problem.

Subaru engineers seem to think that 30wt (at operating temperature) is what is needed. 60wt oils are not one of the options. Maybe the engineers are completely wrong, but that's a big leap I would not take.

Back to the OPs original question, another solution might be to add a dedicated oil cooler (the round thing above the oil filter is really an 'oil warmer'). The downsides include the cost and extra plumbing, which extra plumbing may leak (and Subaru engines are leaky enough without any help). An added benefit is that you are increasing the oil capacity slightly. Almost any engine, Subaru or otherwise, would benefit from an oil cooler. Car makers have concluded they are generally unnecessary, but that doesn't mean they would not be beneficial.
 
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