Let's talk oil temperatures on the street

Earlier this year, I added a Mishimoto oil cooler & AEM oil temp gauge to my S2000. The car is mechanically stock, I only added the oil cooler in order to keep oil temps down during open lapping days at High Plains Raceway. Worked just fine! Highest oil temps I saw this summer at HPR was about 240 F.

The only thing is, since I primarily drive my S2000 on the street, I'm a bit concerned with my oil temps being low. For reference, during normal street driving, I'm only hitting temps in the high 190's F on average. Occasionally I'll run through the gears and get them a bit over 200 F, but generally only 190's. On cool nights, this sometimes drops into the high 180's.

I'm using a 200F thermostat with the oil cooler, but with the temps I'm seeing, I'm pretty sure it's opening up prior to 200 F.

I feel like these temps are just a bit too low on the street and I'm thinking about removing the oil cooler.

If I'm being honest, I'm not sure if I'm going to attend anymore HPDE open lapping days in the S2000 anyway. I've been considering just buying a budget beater track car that I don't care about for track days; something I can afford to lose if something breaks or I wreck it. At that point, I would just be using my S2000 for street driving, canyon carving and the occasional autoX event.

Since that's the direction I'm considering with my S2000, I figured if the oil cooler wasn't hurting anything, I would just leave it in... but if the low temps might have long-term adverse affects, I would remove it. I've heard that you should try to get your oil temps around ~212 F in order to burn off water/moisture; any truth to that?

Thoughts? Recommendations?

Instead of removing, why not just ziptie some cardboard around when on the street.

Thermostat's don't stop all flow.

Anywhere around 190+ is good enough IMO. Water will evaporate below the boiling point, just not as quickly. If you weren't getting over 180, I'd be worried.

It's possible that in some driving you're never getting the oil hot enough to open the cooler t-stat at all (in which case, it would show the same temps without the cooler).

I've IR-gunned the oil pan on my Jeep and gotten temps in the 190s after driving around town with no cooler. I've seen it as low as mid-high 180s in the winter. Run it on the highway and the temps will come up into the 195 - 210 range. Running it hard warms it up more.

Personally, I'll be running an oil/water cooler as that will keep the oil from ever running below 190-ish (coldest the coolant will get when fully warmed up on a sub-zero day).

Where's your oil temp sensor?

You ideally want it in the 200~220F range. If you really think it's getting too low but you're still using the car on track, don't remove the cooler, just make a cover for it for street use.

Sounds like the thermostat isn't working properly. If you can't get the temps up during normal driving, then yes, remove the cooler.

There is truth to it being bad not getting your oil up to and past the boiling point of water.

In reply to z31maniac:

That's not a bad idea. I would prefer the car not look like it has a piece of cardboard stuck behind the lower bumper opening, but I suppose I can probably rig something up and see how much it affects oil temps.

In reply to roninsoldier83:

Use black coroplast or some cheap black paint on the cardboard.

NEALSMO wrote: Sounds like the thermostat isn't working properly. If you can't get the temps up during normal driving, then yes, remove the cooler. There is truth to it being bad not getting your oil up to and past the boiling point of water.

Thermostats always allow some flow past, even thermostats for radiators.

GameboyRMH wrote: Where's your oil temp sensor? You ideally want it in the 200~220F range. If you really think it's getting too low but you're still using the car on track, don't remove the cooler, just make a cover for it for street use.

The temp sensor is in the sandwich plate that connects the oil cooler (OEM oil filter location).

I'll probably make a cover, just to see how much of an effect it has on temps.

I second the "where are you measuring" question. That is, it's in the sandwich plate, but is it measuring the oil going to the cooler or coming back from it?

NEALSMO wrote: Sounds like the thermostat isn't working properly. If you can't get the temps up during normal driving, then yes, remove the cooler. There is truth to it being bad not getting your oil up to and past the boiling point of water.

From my understanding, a lot of the aftermarket oil temp thermostats are more or less "best guess/close enough" temperature rated. I picked the highest one I could find (200 F) for street use, but the thermostat never fully stops the flow of oil to the cooler in this type of design.

The oil comes up to temp pretty quickly, so I feel like the thermostat is staying closed (as much as it can be) until around 185-190 F. I don't think it's defective per se; I think that's just the way it is.

On my 911 you can actually watch the thermostat open and close as it warms up and then gets a surge of cool oil and then closes again until all the oil has circulated and is warm. It does have a considerable volume of oil away from the crank case though so that might not happen on your car?

mazdeuce wrote: I second the "where are you measuring" question. That is, it's in the sandwich plate, but is it measuring the oil going to the cooler or coming back from it?

It looks like it's measuring the oil temp from the line closest to the "far end" of the oil cooler; so coming back? To be honest, that's just my assumption, I can't recall the flow direction of the cooler for certain; but the line closest to the sensor is going to the "far" end of the oil cooler.

Stefan wrote: In reply to roninsoldier83: Use black coroplast or some cheap black paint on the cardboard.

I'll keep that in mind, thanks!

Photobucket says I can't see the pictures.
I'd figure out how the oil flows. If it's measuring coming back then I wouldn't be at all surprised if it was 20 degrees colder than it was coming out of the engine and if that's the case, you're actually in the ideal window.
That and your engine oil temps on track are actually higher than you think. So kind of important either way.

mazdeuce wrote: Photobucket says I can't see the pictures. I'd figure out how the oil flows. If it's measuring coming back then I wouldn't be at all surprised if it was 20 degrees colder than it was coming out of the engine and if that's the case, you're actually in the ideal window. That and your engine oil temps on track are actually higher than you think. So kind of important either way.

Hmmm, showed up just fine for me...

Does this image work?

Yup, that one works.

If you don't want to go cardboard or coroplast, make up a nice thick vinyl muff you can attach around the cooler with Velcro. It works for diesel trucks in the winter when they block off the grill, it should work for you

I'd confirm whether the sensor is reading the temp before or after the cooler before you change anything. If it's after, your temps are fine. If it's before, a hair warmer would be nice, but you're not cold enough to worry IMO. Especially if it doesn't go colder in cooler weather.

Based on the photos of the sandwich plate, the sensor looks to be on the opposite side of the thermostat (which appears to be be going to the oil cooler). So, it looks like the sensor is positioned after the incoming/return line from the oil cooler. So, the engine's oil temps are probably a bit higher than my temp gauge is reading; which would mean the thermostat is likely working as designed.

I wonder how much of a difference there is between the incoming/out-going oil temps...

In reply to mad_machine:

That's something to look into! Thanks!

In normal driving including 75-80mph cruising my FR-S and Cobalt SS both run in the 190's. The temps don't come over 210 until I start doing a lot of full throttle running.

In reply to parker:

Good to know! Just seemed low to me. My current daily (Focus RS) appears to run just over 200, but it's hard to tell with the tiny, not clearly labeled OEM analog gauge. My last car (Golf R) had a digital oil temp gauge that measured 225-230, and my WRX before that had a digital oil temp gauge that read 215-220. So, I guess I'm just used to seeing higher oil temps on the street.

It definitely depends on the engine. Some will heat the oil more under light load than others. If you've got an IR gun handy, see what the outside of the pan reads while idling after a drive and compare to the gauge reading just to satisfy some curiosity.

roninsoldier83 wrote: In reply to parker: Good to know! Just seemed low to me. My current daily (Focus RS) appears to run just over 200, but it's hard to tell with the tiny, not clearly labeled OEM analog gauge. My last car (Golf R) had a digital oil temp gauge that measured 225-230, and my WRX before that had a digital oil temp gauge that read 215-220. So, I guess I'm just used to seeing higher oil temps on the street.

Yeah, my 540it runs pretty hot too— 210 normally and 220-230 when I'm beating on it. Apparently that's normal. The coolant also runs at 226, thanks BMW!