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2019 Subaru Forester Premium, Crystal Black Silica, Pkg 15
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Discussion Starter #1
I've been monitoring my temperatures with the OBDLink LX paired with an Android phone using ActiveOBD. I love the program. Everything works great.

My commute to/from work is about 10 miles, mixed between about 5 miles of highway driving followed by 5 miles of city driving. The speed limit on the highway is 55 (I'll usually do 60-65...) and the city portion is 40 and 35. During the morning commute, I drive so early there's few other cars on the road, so I don't have the stop-and-go of city driving. On the way home, though, I usually seldom can get up to the 40 mph speed limit due to lights and traffic.

I've been noticing that my oil temperatures are getting up towards 195-196 F by the end of the ride, coolant temperatures are getting up around 200-205 F. Unfortunately, before this program, my Gen4 doesn't have a temperature gauge for my coolant like my Gen4 Legacy did, so I only get the blue/red "caution" lights on the dashboard as applicable.

That got me thinking about coolant temperatures, which then got me thinking about head gaskets. While my Gen4 does use the newer MLS head gaskets, it also is still an EJ, so I'm keeping an eye on it, more out of paranoid maintenance instilled into me during my ownership of my Gen4 Legacy, which eventually had an issue.

I know that HG problems are often caused by heat, and possibly corrosion from acidic coolant. My Legacy used the green coolant, and now my Outback has the Super Blue coolant, which is supposed to be good for over 100k miles. But, I'm wondering about the whole acidity aspect, and maybe I should accelerate my coolant changes.

But I wouldn't know what to look for. I know that the boxer layout does keep a portion of the heads saturated with oil/coolant compared to the V6/Inline style where gravity will pull it downwards. I believe this is contributory to their relatively aggressive 60k spark plug change interval.

So, now that I have the means and ability to keep an eye on my coolant/oil temperatures, how hot is a problem? When does the red warning light illuminate? Is it worth changing out the super blue early due to acidity concerns?

Regarding oil temperature, is my ride long enough to get rid of the unburned fuel via PCV or should I keep changing my oil on the quasi-severe service schedule?

I'm running Mobil 1 High Mileage 5w30 with a tentative 5,000 mile or 6 month interval, whatever is first. I drive just about 10,000 miles a year. But, if the unburned fuel gets encapsulated by the oil and doesn't get up to temperature where it can be burned/evaporated off, I'm thinking I might need to change it more often.

I can also adjust my commute to do one or two days a week on a toll highway that would be about 15 miles of highway and about 2 miles on each side doing suburban-type driving once I'm off the highway, if that could be more helpful to the engine.

While we're on the topic of monitoring temperatures, when is an engine "warm"? I try to keep it below 3,000 RPMs unless it's an emergency when it's cold, but again once that blue light goes out, I previously had no idea of the temperature. Should I be looking for a specific oil or coolant temperature before I start driving a little "harder?" Back to the whole HG topic above, that whole thing is under a lot of stress if you start running it hard before everything's up to temperature, putting more pressure on the HG's.

Thanks!
 

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I recall a temperature thread a while back. 180-200 is on the low side for most modern engines. Going from memory 200-220 is pretty typical warmed up under load temps. Where it starts getting dicy on things I recall around 250 starts to approach early failure levels of fluids which then can escalate temps and whatever the cause to get that high just snowballs the over heat situation.
 

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2019 Subaru Forester Premium, Crystal Black Silica, Pkg 15
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Discussion Starter #3
I'm curious to see how summer and highway temperatures change the fluid temperatures. What's your opinion on the whole severe service for short trips thing? From the things I've read (on any car), the unburned fuel/exhaust gets encapsulated in the oil and eventually gets burned off/evaporated when it gets up to full operating temperature. I'm thinking since I seem to be hitting an oil temperature plateau around the 190's that it would be okay on my 4000-5000 mile OCI?
 

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2018 Outback 2.5i Limited Eyesight - Remote Start - Auto Dimming In/Outside Mirrors
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My car typically floats between 210 and 220 from an oil temp perspective. I have heard with water boiling at 212, modern engines like to keep oil in that range to help burn off any moisture build up.
 
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