"Best" operating Oil Temperature

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I did a search for this and didnt find it so pardon if i am asking a FAQ.

What is the optimal (best) operating temperature for engine? Is the best operating temp different between engines, say gasoline vs. diesel?

Opinions?

Darrell
sin city
 
IMO, the safe zone for oil temperature is 190-220F. Anything lower and you risk not getting all the moisture out. Anything higher and you're oil is going to degrade faster.

[ November 23, 2004, 04:15 PM: Message edited by: Patman ]
 
Your header asked for oil temperature, then your question asked for engine temperature. There is no single "engine" temperature. There is oil in the sump, oil from the cooler (if fitted), coolant in the head, cooled coolant exiting the radiator, etc.

Oil should be normally warm...I'd say 180-220°F. Perma-Cool sells a thermostatic bypass valve for oil coolers that begins to open at 180.

Coolant?...what ever the OEM thermostat temperature is.


Ken
 
Circle track racers: "Running higher coolant temperatures makes sense if you can control it, but what effect does the higher temperatures have on oil temperatures? Evans' answer comes from his testing with Detroit's automakers. Evans said, "Chevrolet is now saying we should be running the oil temperature at 220 to 240 degrees. If you're not, you are giving away horsepower. We have learned to stay below 260 to 270 degrees because the life of the oil starts to fall off. The people who run 180 degrees need to know that it is not good for the bearings. The oil is too thick. The rings are plowing through it and the pump is pushing it, both of which rob horsepower."
http://www.evanscooling.com/articles/aug97ct.htm

"For the best performance, water temperature should be in the range of 200-210 degrees F...The temperature range of the engine oil should be 220-230 degrees F." http://www.circletrack.com/techarticles/1822/

Info on diesel engines here:
http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=1;t=008311
http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=008233#000000
 
quote:

Chevrolet is now saying we should be running the oil temperature at 220 to 240 degrees. If you're not, you are giving away horsepower

This would assume that thermal energy is being shunted from the combustion process through the oil. Some engine builders coat pistons and combustion chambers with powder coatings that insulate the combustion process from exiting via the head or the piston. The oil, I would imagine, would soak up this naturally otherwise wasted heat.

Should everyone with auxillary oil cooler squirters turn them off for the sake of thermal efficiency??

quote:

The people who run 180 degrees need to know that it is not good for the bearings. The oil is too thick. The rings are plowing through it and the pump is pushing it, both of which rob horsepower."

This is only under the assumption that "that" oil is at the proper visc at that higher temp ..and that another oil would be at an improper viscosity at 180°F. If I want to run a low 20weight oil ..that is totally out of the question for the viscoisty requirements of the engine @ 250°F ..but is IDENTICAL to a 40 weight @ 180°F ...how can this assertion be true ..or how can I be harming anything?? This is where these assertions lose credibility for me. What viscosity is any oil on a sliding scale that it has never been tested at? If you are going to ALWAYS run your oil @ 270°F ..then a 60 weight MAY fill the bill for THAT engine. That "just happens to be" viscosity may end up being a lower visc oil at a lower temp. How does this flush in these peoples heads
dunno.gif


The point I'm making is that there are some arbitrary assertions here that are only truth under certain condtions. The 220-240°F assertions may apply to current trends in OCI and in the context of energy policy along lines of preferred and prescribed maintenance schedules ...and whatever models that they currently employ for longevity.
 
quote:

Originally posted by Gary Allan:

quote:

Chevrolet is now saying we should be running the oil temperature at 220 to 240 degrees. If you're not, you are giving away horsepower

I agree with your skepticism, Evans is selling higher engine operating temperatures to justify the use of their coolant. Follow the money.

Oil, elastomers in hoses, plastics on the engine all break down faster at higher temperatures.

They are right about running oil cooler giving away horsepower, provided it's the same SAE visosity and I think that's what they meant. That;s because it takes more force to shear thicker oil.

As you so ably described later in your post, actual viscosity varies with temperature. You can get the same kinematic viscosity at a lower operating temperature by using a different SAE viscosity oil, so their claim about cooler oil giving away power is largely bogus.
 
Thanks for the responses. I was actually wondering about oil temperature more than anything. Specifically, i ride a harley that has seperate systems for transmission and engine. They run a oil tank for engine oil and its very common to run a oil temp gange in the tank. I have a thermostatically controlled oil cooler installed and the oil in the tank usually runs between 175-200 degrees. Obviously i think the oil temperature while circulating is hotter, i just didn't have a clue what the best oil temp is.
 
quote:

Originally posted by LVHospiceRN:
They run a oil tank for engine oil and its very common to run a oil temp gange in the tank. I have a thermostatically controlled oil cooler installed and the oil in the tank usually runs between 175-200 degrees. Obviously i think the oil temperature while circulating is hotter, i just didn't have a clue what the best oil temp is.

A Harley's oil tank is pretty analagous to a wet sump engines oil pan. It's a good place to take the temperature because just about all oil temp data for engines is based on sump temps.

175F is a bit on the cool side, but as long as it frequently gets over 180F and stays there a while it should be OK.
 
quote:

Originally posted by Gary Allan:

quote:

Chevrolet is now saying we should be running the oil temperature at 220 to 240 degrees. If you're not, you are giving away horsepower

This would assume that thermal energy is being shunted from the combustion process through the oil. Some engine builders coat pistons and combustion chambers with powder coatings that insulate the combustion process from exiting via the head or the piston. The oil, I would imagine, would soak up this naturally otherwise wasted heat.

Should everyone with auxillary oil cooler squirters turn them off for the sake of thermal efficiency??

quote:

The people who run 180 degrees need to know that it is not good for the bearings. The oil is too thick. The rings are plowing through it and the pump is pushing it, both of which rob horsepower."

This is only under the assumption that "that" oil is at the proper visc at that higher temp ..and that another oil would be at an improper viscosity at 180°F. If I want to run a low 20weight oil ..that is totally out of the question for the viscoisty requirements of the engine @ 250°F ..but is IDENTICAL to a 40 weight @ 180°F ...how can this assertion be true ..or how can I be harming anything?? This is where these assertions lose credibility for me. What viscosity is any oil on a sliding scale that it has never been tested at? If you are going to ALWAYS run your oil @ 270°F ..then a 60 weight MAY fill the bill for THAT engine. That "just happens to be" viscosity may end up being a lower visc oil at a lower temp. How does this flush in these peoples heads
dunno.gif


The point I'm making is that there are some arbitrary assertions here that are only truth under certain condtions. The 220-240°F assertions may apply to current trends in OCI and in the context of energy policy along lines of preferred and prescribed maintenance schedules ...and whatever models that they currently employ for longevity.


This must be GM's answer to 5W-20. Just run 5W-30 at higher temps. The phrase "backhanded engineering" comes to mind.

No thanks. If I want a 20 weight I'll use one. Once you're past 100C I don't understand how higher temps would do anything for you but shorten oil life...
 
I have an oil temp gauge in my Kenworth truck (Detroit Series 60 engine) and it seems to stay at about the same temp as the water, but the water temp fluctuates a little more. It also takes the oil a little longer to get up to operating temp. A diesel engine will get really bad fuel mileage when the water temp is too low (stuck open thermostat), even though at times the water temp reaches near 180 degrees. I believe 195 degrees is about the best temp for fuel mileage and emissions. BTW there is a 195 degree stat in the Detroit engine as well as all my cars. As far as I know 195 is the standard operating temp.
cheers.gif
 
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