Ideal engine oil operating temp range

[arghx7]

Originally Posted by Kostamojen

Why these weren't included from the factory, is beyond me...

I apologize if my previous post was too long or too technical and was thus skipped over by many people. The reason why it wasn't included was that the oil temperatures simply do not get high enough for what they expected severe driving to be for most customers. Anything under 270F definitely isn't going to harm anything, although it's not ideal.

The determination of whether it needs an oil cooler is evaluated on an engine dyno, not in a vehicle driving on a track. The reason why it's done on an engine dyno with a guesstimate of speed & load is because by the time you have prototypes driving around, it's too late to make such a decision about hardware. Manufacturing tooling is frozen long before you can get a representative vehicle driving around to see how high the temps actually get.

Also, it's much easier to install good instrumentation in a lab to calculate the heat transfer from the oil and coolant circuits. These heat rejection calculations, measured in kilowatts from mass flow and temperature change of the fluid, are used for sizing of coolers. And they're done way before anyone ever drives the car around in the real world.

[Kostamojen]

Originally Posted by BRZPDX

How effective are these for a fi'd FA20?

These are the stock oil coolers from Turboed factory Subaru motors (this specifoc one is from the Forester and 2015 WRX with the new turbo FA20). Thats exactly what they are designed for.

[calmtigers]

Quick question, would you say a cooler is necessary for someone planning light NA modding (ihe/tune etc) but who lives where it's very hot in the summer? (Gets to 110F, regular 100F)

[kavanagh]

Originally Posted by SirBrass

No thermostat for those of us who are going to get the forester XT oil cooler kit. Oil never flows to an external air/liquid heat exchanger. Rather the regulator core is fed by the engine's coolant lines (not the radiator cold return) & thus integrated into the engine's basic coolant circulation. It brings oil up to temp faster in the cold & keeps it down in the heat.

I just ordered a koyo radiator today. I'll source the forester XT oil cooler parts after my next paycheck.

On phone I am. Therefore, if mistakes I make, Frank Oz blame you should.

@SirBrass I know we're both in AZ where it's friggin hot almost all the time, I appreciate your research on this particular solution.

Do you know (or does anyone else want to chime in) if an upgraded radiator is required/recommended if we decide to go this XT oil cooler kit path? And where are you sourcing the XT parts from - do you have part numbers yet?

Also, does anyone know of a similar solution for cooling the automagic transmission? I know there are external radiator options, but this seems more elegant and possibly lighter weight.

[SirBrass]

It's not hot all the time. Really. Objectively we don't have temps which during the year exceed those elsewhere. Except for the next several months.

I don't think a street car will need an upgraded radiator, but I'm going to do it anyway as a precaution. And because the stock radiator is so stupidly thin.

I'm going to follow the DIY recommendation on where to source the parts for the oil cooler from. I've already ordered a koyo radiator from Camelback performance ($300 + approx $20 tax). Should be here this week. I won't install till I have it all together.

I only want to take my bumper off once.

On phone I am. Therefore, if mistakes I make, Frank Oz blame you should.

[SirBrass]

DIY for the XT oil cooler: http://www.ft86club.com/forums/showthread.php?t=50427

On phone I am. Therefore, if mistakes I make, Frank Oz blame you should.

[Tye300]

Originally Posted by calmtigers

Quick question, would you say a cooler is necessary for someone planning light NA modding (ihe/tune etc) but who lives where it's very hot in the summer? (Gets to 110F, regular 100F)

If you plan to track regularly then yes you need one. If your just going to mod and drive it spiritedly on the street or mountain roads, no. If you want to have peace of mind, get one. Personally I have not reached alarmingly high oil temps on the road. On the track, it's a different story.

[plucas]

Anything under 275 degrees F is fine and I would not worry.

[kavanagh]

Originally Posted by SirBrass

*snip*

I don't think a street car will need an upgraded radiator, but I'm going to do it anyway as a precaution. And because the stock radiator is so stupidly thin.

*snip*
On phone I am. Therefore, if mistakes I make, Frank Oz blame you should.

we've begun tracking the car on a somewhat regular basis, so an upgraded radiator may be in our future as well. I'd like to see yours when it's done. In fact, let me know if you want a hand with the install - I think we're pretty close to each other.

Originally Posted by Tye300

If you plan to track regularly then yes you need one. If your just going to mod and drive it spiritedly on the street or mountain roads, no. If you want to have peace of mind, get one. Personally I have not reached alarmingly high oil temps on the road. On the track, it's a different story.

I read through your whole build quite a while ago Tye, I forget, did you do a transmission cooler as well?

[Tye300]

I read through your whole build quite a while ago Tye, I forget, did you do a transmission cooler as well?

Not yet. I'm looking closely at the SSP offering, although I think it is worth it, I want to see if there is a cheaper solution with the B&M cores. Looking under the AT, there is a heat exchanger beside it. It connects to the block which runs a coolant line through it. I want to explore if running a B&M core inline with it would help. The SSP cooler includes an oil pan with a sender and return line via pump to a core to directly cool the ATF. This is the best option. Maybe I can get a spare AT oil pan and build my own kit using a B&M or setrab core.

The OEM heat exchanger is on the left side of the transmission oil pan here:

[Kostamojen]

Originally Posted by kavanagh

[MENTION=62167Do you know (or does anyone else want to chime in) if an upgraded radiator is required/recommended if we decide to go this XT oil cooler kit path?

No its not needed.

[Tye300]

@kavanagh,
Have you experienced the AT shifting by itself at redline when temps get too high at the track? It usually lets you bounce off the limiter until you shift when temps are cool, but when temps get high, it shifts by itself at redline. The shifts feel softer also during this. Must be a safeguard to protect the transmission.

[kavanagh]

@Tye300 we haven't seen that yet in our auto. Probably because I try to shift a hair before redline. We're going back to the track 31st May, so I'll see if Lisa or I can reproduce it then. I bet you're right and it's a safety measure.

[Gords_zenith]

I'm going to drop this here again. The main thing to consider which I think most do, is the fact that oil becomes thinner with heat (viscosity lowers), but what I want to stress as @Dezoris did was that you have to have the ideal weight of oil for the temps you will be running. Which I think most here understand but its good to re-emphasize. So when people give blanket statements saying 275F or 132C is safe they need to understand that yes the "oil" is fine but now you are risking your engine because the factory 0W-20's viscosity has dropped out of the engines optimal design range - I'm deducing this based on the weight of oil Subaru spec'd from factory. So looking at my link you can see the relationship of the different weights of oil vs temp. And from this you can make a better judgement if you should simply up the weight or run an oil cooler. The stock engine from reading everyone's UOA on stock oil seems to around ~7cST @ 100c so in saying that - our engines optimal protection range is from 5.6 to 9.3 cSt @ 100c based on the American petroleum institute website. Again, once temps start getting to 125-130 C with 0w-20 you are running your engine dangerously close to the fine edge of protection and could risk bearing damage when pushing it. In my post there is a link where you can input the oil that your thinking of running using its viscosity index and then click the temp range that you want the graph to start at ex) 95 degrees Celsius is a good starting point.

http://www.ft86club.com/forums/showthread.php?t=63955

I hope my post was clear as mud and can be useful to people. I've struggled with determining a good oil to run and have recently went through painstaking process of trying to educate myself on it and therefore make a better choice. In saying that I think I'm going to run Mobil 1 0W-20 again as I don't track my car and the highest temps I've seen are 120C while back roading and if during the summer it starts to get too hot I'll get the forester XT OEM cooler or run a thicker oil. Good luck.