Post HPDE oil temp update

bmcd308

My stock 370Z ran oil temps in the neighborhood of 215 to 225 in normal driving, and after reading many posts here, I decided that I wanted an oil cooler before doing a HPDE.

I live reasonably near Z1, so I had them install their 25-row oil cooler with thermostatic plate. The result was oil temps in normal driving situations of 175 or so.

This weekend, I did my first HPDE at Road Atlanta. I had a blast, and I thought I'd post my oil temp observations just to memorialize them here.

On the freeway trip to ATL (2.5 hours at 75 MPH using cruise control) at 80 (departure) to 74 (arrival) degrees, my oil temp stayed at 175-180 for the whole drive. During the HPDE, when the ambient temp was 90-95 degrees, my oil temp went up to 225-230 by the end of each 30-minute track session.

On the drive home on Sunday, with ambient temps cooling over the drive from 90 to 80, my oil temp fell slowly from 225 or so (the temperature to which it had cooled while I loaded up) to about 190 on the drive (75 MPH cruise control).

From this, I conclude that a 25 row cooler is overkill for daily driving and light track use. I feel like Road Atlanta is a pretty good test of a cooling system, and this past weekend was pretty hot.

I would have been comfortable with track session oil temps closer to 250 for occasional track days, and I want my oil temps over 180 during DD. I am going to have to use a plate to reduce the efficiency of my oil cooler for DD, which I do not really mind, but this experience may provide a different perspective for someone in my situation choosing between a 19-row, a 25-row, and a 34-row.

Note that I do not know whether a 19-row would have been a better choice for me. If I had a 19-row, I might be on here complaining about high oil temps despite my oil cooler.

Brent

DR_

Most motor oils works best at 180-210 so DD oil temps of 180 are perfectly fine IMO. I have a 25 row and my DD temps during the summer are about 200 and my track temps are around 250.

robones

I agree with OP. You want your Oil temps around 200-220 for maximum engine efficiency and cleanliness. Colder temperatures, introduce oil sludge, degrade in MPG and harsher startups over time. 180 is wayyyyyy too cold for DD. Unless you are a serious track nut, you do not need an oil cooler.

ChrisSlicks

Brent, you're oil temps on track will start to get higher as you start getting better, faster and driving harder on track. It won't be unreasonable to hit 250 plus on track with your setup. Definitely not overkill for the track, just a little bit for the street.

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SPOHN

^+1

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DR_

Why do you think 180f is too cold for DD if the stock coolant thermostat is set to open at that temp? The engine is designed to get to 180f as quickly as possible and then stay as close to that the best it can.
If you let the engine sit the oil won't get any warmer than the coolant temps, which won't get any warmer than the thermostat temp. Oils are at their rated viscosity at 212f (100c) but the factory obviously feels the oil is close enough at 180f to effectively lubricate. So I think 180f-212f is the safe oil temp zone for a DD. Anything less and I would suggest you change something in your setup.

ChrisSlicks

Coolant thermostat starts opening at 180F but isn't fully open until 200F by my measurements (reading coolant temp on OBDII). Cooling fan kicks on at around 220F.

The viscosity of 5W30 at 180F is approximately twice that of oil at 210F. It isn't going to hurt anything but you are losing some efficiency.

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DR_

Good info. My thermostat seems to fully open a little sooner at about 196f. Also what numbers are using to come up with twice as thick at 210f? The SAE viscosity curve charts I've seen show about 15 cSt at 180f and 10.5 cSt at 210f but good synthetics should be much closer. I'm not a chemical or mechanical engineer (my wife is a CE), but I'm interested in the subject.

ChrisSlicks

Sorry I misspoke. I was thinking 50% but during brain translation it come out as double, I apologize.

Yes, that is the same calculator I use for my rough analysis. You can enter specific values from manufacturer data and it gives a pretty reasonably accurate plot. Interestingly enough the difference in viscosity between conventional oil and synthetic isn't all that (statistically) significant.

I'm not an oil expert either, just have a strong interest in the subject as I would like to keep my car alive on track

I had been toying with the idea of going up a step in viscosity since I was spending so much time at elevated temperatures, but I think the real solution will just be to figure out how to improve cooling.

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Hotchkis ARB | Stillen CAI | Art Pipes | Berk CBE | Stillen AP Racing Brakes | AE Performance Oil Cooler | BC Racing ER Coilovers | Doran Control Arms

DR_

Well you are in the NE which helps a lot on the track. Here in Texas most of our track days are in 85f+ temps. I've done races in over 110f+ temps and it is just brutal on the car (and driver). I haven't done much on track with the Z yet but the plan is to sell the race car and modify the Z to be capable to do several track days a year.

ChrisSlicks

I do about 14-15 days currently, and yes in the early spring and the late fall when temps are cooler everything runs nice and smooth. Once the temp gets over 80 things start getting pretty hot, and at 85+ there is a noticeable drop in HP and lap times (due to traction and HP), water and oil temps start climbing quickly. Can only go about 10 minutes before having to give it a break in those conditions, in Texas it would be far worse.

If you're going to do a fair amount of track buy the largest oil cooler you can, run a block off plate when DD'ing. Since the oil cooler by itself isn't keeping up for me I'm going to upgrade the radiator, and go to a vented hood to help increase air flow through the radiator, and increase the oil line size for more flow since the AE kit came with -8AN lines.

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370Z Purist

This is an ideal solution. I believe it was Shadoquad that fabbed up a block off plate from an aluminum sheet and affixed via velcro. Seeing as he drives in a temperate area where the ambient temperature drops to 30-40 degrees during the spring and fall, you'd have to try pretty hard to push temps past 180, especially during rain. Going to the track? Tear off the plate and drive it like you stole it.

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