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Here in Tucson Arizona, most summer days get up to 109F degrees.
Which is the best oil viscosity for these hot desert climates?
I plan on using synthetic Mobil 1

2017 Outback 2.5
 

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Here in Tucson Arizona, most summer days get up to 109F degrees.
Which is the best oil viscosity for these hot desert climates?
I plan on using synthetic Mobil 1

2017 Outback 2.5
Per manual 0w20. Its perfectly ok to go up one level in viscosity 5w30 during the hot summer month. During the winter months you may want to go back to 0w20.
 

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IMHO, I would not change viscosity between season, stick with 5W30, Mobil1 is probably the best choice.
 

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I am curious to know what might have lead you to believe that 0w20 would not be adequate for the temperatures you are experiencing?

If you are going to use a 5w30 from Mobil 1 I would recommend the Extended Performance version and submit for a $12 rebate while you are at it.
 

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I'm a believer in that part of the manual that allows a thicker viscosity depending on conditions. In AZ, in that area, a 0w oil is of no value so I'd run the Pennzoil 5w-30 that's a really watery 30 but likely very good for those alternate conditions the manual had in mind.

I have no qualms about running a nice 20 in AZ but if I was standing in the oil aisle of Walmart, I'd pick up something x-30.
 

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In the manual it dose not even list 5w30 as am option for the 2.5. Going to a thick oil will not give better protection as one may think. 90% of engine ware is in the first min. of start up and that is why the 0w20, for oil flow on engines with tight tolerances. It's all in the additives that makes a good Engine Lubricant with high engine protection.
 

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Consider that ambient temperature has very little effect on the engine oil temperature in a fully warmed up water-cooled engine. Of course, this assumes that the engine cooling system and thermostat are working correctly, so the coolant temperature remains relatively stable.

FWIW, the engine oil temperatures in our 2015 Legacy and 2016 Outback (both 2.5s) stabilize during constant-speed highway cruising at about 15 degrees F above coolant temperature in winter, and about 25 degrees F above coolant temperature on 90+ degree summer days. Thus a ~60 degree difference in ambient temperature results in only ~10 degrees difference in engine oil temperature.
 

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In the manual it dose not even list 5w30 as am option for the 2.5. Going to a thick oil will not give better protection as one may think. 90% of engine ware is in the first min. of start up and that is why the 0w20, for oil flow on engines with tight tolerances. It's all in the additives that makes a good Engine Lubricant with high engine protection.
The manuel lists the recommended viscosity but later on it specificlly says that oil with a higher viscosity may/can/is necessary in certain conditions, among them high temp.

You've been here for 6 months however there are many threads and discussions about how the manual isn't clear on quite a few things, oil viscosity among them.

If you want to scratch your head, read a 3.6 manual that says conventional is recommended but that a syn oil gives better performance. They don't say what that performance gain is or where it comes from and it also begs the question of why SOA would recommend a lesser performing oil.

In my UOAs, now covering almost 82k miles, only two of my changes have used the viscosity and grade recommended by the manual and all of them have been more than fine. The manual is not gospel on oil. It's almost a starting point for those who want to tailor their oil to their use.
 

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... it also begs the question of why SOA would recommend a lesser performing oil.
Simplified explanation: The 3.6 engine and its running clearances appear to have been designed around the physical properties of conventional refined-petroleum oils available at the time. That was more than 25 years ago, and engine oils have improved significantly since then and are much more widely available, especially mainstream synthetics.
 

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If your oil temps go at or above 230 it makes sense to consider bumping up a viscosity grade.
 

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Simplified explanation: The 3.6 engine and its running clearances appear to have been designed around the physical properties of conventional refined-petroleum oils available at the time. That was more than 25 years ago, and engine oils have improved significantly since then and are much more widely available, especially mainstream synthetics.
That's as good of an explanation as any and that also supports the idea that the OM is pushing outdated recommendations. It also supports some research on what were typical 100C viscosities back then as compared to now. I'm thinking they were thicker back then as a general statement which might mean or could mean that thicker oils are still blessed. I'll see what I can dig up. It might help or just lead to screams of anguish.

Why would a 3.6 owner try to find a conventional when you can find Supertech or Kirkland fully synthetic oil that is very inexpensive? There's no reason to run a conventional.
 

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If your oil temps go at or above 230 it makes sense to consider bumping up a viscosity grade.
This is a very good point, I am concerned right now with the fact that in my current experiment of running 5w20 instead of 0w20 the operational oil temperature is regularly bordering 230 degrees. The oil temperature never got close to 220 degree, under any circumstance, running 0w20.

Also the one time I experimented using 5w30 the car ran sluggish with slightly higher oil temps as well. I am not convinced that running a 5w20 or 5w30 is or will be some magic bullet for this engine.
 

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I am concerned right now with the fact that in my current experiment of running 5w20 instead of 0w20 the operational oil temperature is regularly bordering 230 degrees. The oil temperature never got close to 220 degree, under any circumstance, running 0w20.

Also the one time I experimented using 5w30 the car ran sluggish with slightly higher oil temps as well. I am not convinced that running a 5w20 or 5w30 is or will be some magic bullet for this engine.
I'm going to change from 5w-30 to 0w-30 this weekend and will report back if anything seems different, e.g. higher or lower oil temps.
 

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So, yours truly went back in a time capsule to see what the grades of oil were around 25 years ago and the time machine says that SH and SJ were ending and starting but the physical properties of the oil within the 30 wt oils remain the same today as they were back in yesteryear.

An oil meets viscosity for a 30 if it's is no less than 9.3 cSt and no more than 12.5 cSt at 100C That's a lot of range to fall into and certainly it's not a narrow band.

Pennzoil Platinum is almost a 20 oil with a 9.X value while most other oils are in the mid to high 10 range. At the upper end you'll find some M1, Redline and Castrol oils that are close to 12 if not over but those higher end oils tend to be A3/B3-4 rated and almost onsidered a thin 40. That may not be a bad thing at all.

A lot people run M1 0w-40 where a 30 is called for and you can see why they do it. It has among the most stringent approvals, a very high TBN value of 12 and it's an A3/B4 oil. It has a stated 12.9 cSt value which you can see is very close to a 30. In my car oil shears, dilutes down about .8 so that means right away after an oil change the oil is marching to 30 grade.

For this coming Satureday's oil change, I going to use use M1 5/30 SN+ which starts off at 11.1 and ends up, like it did before, at around 10.3 thus it's still firmly a 30 with lots of room to spare.

Enough of my time travel.

I'd still use a thin 30 in AZ or if one must insist on a 20, something like RL which is almost a 30.
 

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I'm going to change from 5w-30 to 0w-30 this weekend and will report back if anything seems different, e.g. higher or lower oil temps.
Wut you talkin bout, Willis?

Nothing will change with that viscosity so you must have meant going from x/20 to a 0/30.
 

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Nothing will change with that viscosity so you must have meant going from x/20 to a 0/30.
The 5W-30 in the engine now is Amazon Basics so it's a full-synthetic generic, and the 0W-30 will be Pennzoil Maximum Power, a semi-premium synthetic. I wouldn't attribute any changes to the 0W vs 5W necessarily - it could be other additives or base stock formulation issues aside from winter viscosity which doesn't really apply to us in Hawaii.

The shocking thing is Kevin's 10 degree increase going from a 0W-20 to a 5W-20. I did not experience that difference when I went from the OEM/Idemitsu 0W-20 to Amazon Basics 5W-20, nor did I get a significant temperature bump moving to Amazon Basics 5W-30, but in the spirit of empiricism, I'll report back any changes. So far my results have been that viscosity doesn't significantly increase oil temperatures but Kevin's experiment seems to be an outlier. 10 degrees is eye opening. Our engines are also different.
 

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The 5W-30 in the engine now is Amazon Basics so it's a full-synthetic generic, and the 0W-30 will be Pennzoil Maximum Power, a semi-premium synthetic. I wouldn't attribute any changes to the 0W vs 5W necessarily - it could be other additives or base stock formulation issues aside from winter viscosity which doesn't really apply to us in Hawaii.

The shocking thing is Kevin's 10 degree increase going from a 0W-20 to a 5W-20. I did not experience that difference when I went from the OEM/Idemitsu 0W-20 to Amazon Basics 5W-20, nor did I get a significant temperature bump moving to Amazon Basics 5W-30, but in the spirit of empiricism, I'll report back any changes. So far my results have been that viscosity doesn't significantly increase oil temperatures but Kevin's experiment seems to be an outlier. 10 degrees is eye opening. Our engines are also different.
Ah. Now I get it.

The newly revised M1 0/30 AFE is at 11.5 cSt which is up from 10.9 or perhaps it was 11 a few months ago.

Yeah, the Kevin factor... Don't know what to say except that you know he has a parrot on his shoulder a lot of time? It's hard to focus on him as a person when you're cheering for the bird to make a deposit or something like that. Or maybe not.
 

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Yeah, the Kevin factor... Don't know what to say except that you know he has a parrot on his shoulder a lot of time? It's hard to focus on him as a person when you're cheering for the bird to make a deposit or something like that. Or maybe not.
What? 😦

Here all this time I thought the bird in the pic was Kevin. I've often wondered who the other dude was.
Learned something new today.
 
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