normal engine oil temp?

[sneakboxer]

I'm killing time by looking up viscosity charts and i'm wondering what temp my oil is at. I have a 98 jeep w/ a 4.0 i6, 5speed, 2in lift on 31in tires and a 04 civic 1.7 auto bone stock. I drive the car gently but the jeep might get beat a little bit. I'm in Hawaii so the air temp is 65to85 all year depending on elevation.
What do you estimate my normal and peak oil temps are?

I thinking about going from 10w30 to 10w40 or 5w40 in the jeep due to lower pressure at hot idle (10-15psi).
Thanks,
Greg

 

[Gary Allan]

Around 200F+/- 20f depending on load and a minor for ambient. If you're on the highway @ 60 with 4 people in either ..you're probably pushing in excess of 210F ..as soon as you let off the gas ..you will probably be down to 190F.

It takes about 12-15 miles to reach normalized temps ..but you're most of the way there at about 9-10 miles. The last 30 degrees comes on much slower in a non-exchanged engine. That is, the curve really flattens out as you get higher.

Your oil temp may go up a bit if you sit in traffic too long, but I doubt it will out do the high speed temp.

I'd use 5w-40 for the jeep ..and whatever is spec'd for the Civic. If it's 5w-20 ..that's what I'd use.

 

[StevieC]

+1 to Gary

 

[Bruce T]

Fascinating topic! I also lean towards 200°F (93°C) as the center for normal operating temperature, but I've heard AEHaas and bruce381 suggest the ideal temperature is 212°F (100°C). I don't know. Ask an automotive engineer.

I've heard people set the upper limit at 220°F (104°C) or 230°F (110°C). Some even say 240°F (116°C), but that makes me nervous. Few people support 250°F (121°C) for extended periods. Yes, racing vehicles can see 300°F (149°C), but this oil should be changed after hard use. The engine design and synthetic oil are other factors.

On the low end, I've heard some people suggest that normal operating temperature should range from 180-200°F (82-93°C). Of course, this typically comes from companies trying to SELL oil coolers. Ha! Tradition says that 160°F (71°C) is where warm starts, but I don't think it's fully warm until 200°F.

 

[SuperBusa]

I've got a car that has a digital oil temp and coolant temp readout on the dash. I've watched the oil and coolant temps a lot while driving. On the highway just cruising mellow (after reaching full operation temps), the oil and coolant temps are within 2~3 deg F of each other, and hover right around the T-stat setting of 194 deg F.

When you start hammering the throttle hard, the oil temps will start to climb up some, but it takes a while to see the reaction. Same with going back to mellow driving after a hard hammering event ... it takes awhile for the oil temp to come back down. The change in oil temp is not very fast since there is a lot of oil mass changing temp.

Cruising around town will get the oil and coolant temps up into the 215 ~ 220 F range. Obviously in this car (and probably on most cars without an oil cooler), the cooling system is what carries most of excess heat away from the oil. Another good reason to ensure your cooling system is performing 100%. If you ran a cooler T-stat, your oil temps should also stay down some.

Full synthetic oil can take much more high temp abuse than dino oil ... so obviously if you're pushing a car hard for long periods of time (track use), best to use a full synthetic oil.

 

[Captain_Klink]

you need fairly cool oil, like about 200, to carry away heat from the hotter parts of the engine that are exposed to combustion temperatures.

 

[Doug Hillary]

Hi,
sneakboxer - I presume you mean bulk oil temperature - the temperature of the oil in the sump?

If so, most German engine makers appear to aim for somewhere in a band from 93C-100C. Most liquid cooled Porsche engines run at around 93-98C in normal use

Some engines may take up to 30 minutes (or longer) to establish their normal operating equilibrium

It appears that the mid 90s enables good heat transfer in most lubrication systems - but it is all design/application related

Individual oil return lines from turbos etc can show oil temps around 150C as normal

The bulk oil cools at idle (tends to run a little cooler than the coolant) and depending on air flow (and cooling/lubrication system design) most lubricant heats up with load and maintains some sort of design established equilibrium with the coolant

Mineral lubricants start to oxidise relatively quickly at temperatures above 120C

The average coolant & bulk oil temperatures in my 500hp DD powered Class 8 Interstate trucks follow;

Coolant - 93C (engine shutdown occurs @ 106C) Warning @ 100C
Bulk oil - 103C (engine shutdown occurs @ 121C) Warning @ 115C

The shutdown and warning limits are set for mineral lubricants

 

[Gary Allan]

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1146300&fpart=1

Here's a condensed version of some paper that MoleKule did.

 

[FrankN4]

Originally Posted By: Gary Allan
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1146300&fpart=1

Here's a condensed version of some paper that MoleKule did.




From the link:
Quote:
The slope for both RPM ranges was about 0.7 C/C, which means that on the average, the Oil Sump temperature is always 1.2 to 1.43 times higher than the coolant temp.


What did I miss here Gary?

If that is so, it means my 195F normal coolant temperature is indicating an oil temperature of 234F to 278F.

 

[Gary Allan]

Read the rest of the offering. My observations in non-exchanged engines show that oil temp basically follows load. The more you're mashing the pedal (this can be just what it takes going down the highway), the higher the temp will be. You've got natural rejection factors that can be hard to transfer from one situation to another. Keep in mind that the coolant is regulated ..while most oil temps are not. You've got nothing to gauge your thermal throughput for your cooling system in most cases. You can be well within your control range. Those with liquid:coolant/laminar heat exchangers are going to track more closely to coolant temps.

 

[FrankN4]

Quote:
Read the rest of the offering. My observations in non-exchanged engines show that oil temp basically follows load.


DOH

I do not have an oil temp guage on my 4.3 Silverado(yet) but, I would guess that my hottest oil temps would not exceed around 220-225F. This engine has never seen and likely will never see WOT, at any load level, and rarely, maybe 3 or 4 times in its life has seen RPM as high as 2500-3000.

 

[Gary Allan]

Going down the highway is about the highest MOST see, Frank. Basically (and very loosely stated) it's the time compression of the power pulses indexed for the power output at the time. Flog the thing through a few gears to spike it. There you might hang for a bit before coming down, but you're shorting the normalizing event at that output level. Most of us don't drive like that.

 

[XS650]

Originally Posted By: Gary Allan
Going down the highway is about the highest MOST see, Frank. Basically (and very loosely stated) it's the time compression of the power pulses indexed for the power output at the time. Flog the thing through a few gears to spike it. There you might hang for a bit before coming down, but you're shorting the normalizing event at that output level. Most of us don't drive like that.


Freeway grades will show the load sensitivity you mentioned earlier.

If you get into steep grades at lower speeds that require highway or higher levels of power, the oil gets even hotter because of reduced airflow.

 

[Gary Allan]

It's a complicated topic when talking margins where forced and regulated cooling isn't involved.

 

[SuperBusa]

Most cars will see higher oil temps sitting in traffic as compared to going down the hiway at steady speed at 70 mph. I see that happen all the time in my car. As I said earlier, my oil temp basically follows pretty closely to my coolant temp under steady conditions - and there is NO coolant-to-oil cooler unit on this car. If my coolant is at 194~196, my oil is at ~195 on the highway at 70 mph steady state. If my coolant is 215~220 in city traffic, my oil is at ~210.

 

[Gary Allan]

Naturally

 

[Built_Well]

SuperBusa, you really have provided a lot of interesting information in this thread. Thanks for sharing your information with everyone.

May I ask the following: If the coolant has already reached operating temperature (215 to 220* F) after 10 or so miles of city driving and you are now sitting still, just idling the engine somewhere for 5 to 7 minutes, so that your radiator's electric cooling fans have come on, does the coolant's temperature drop quickly? If so, by how many degrees--5?, 10? I'm going to guess that the coolant temp does drop quickly in this idling situation when the fans come on, but it's only a guess.