OIL Temp Question, Your thoughts

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Jun 11, 2002
Clarksville, Tennessee
From another thread on another forum:


Just finished installing my mechanical Oil Temp gauge and wanted to pass along the numbers just incase anyone is interested...

Drove for about 20 miles after the install in 98* Southern California and the absolute hottest it got was 192*.

Drove 18 miles to work this morning at 65* and it barely hit 170*. Cooled down to 160* in traffic. Took like 7-8 miles at highway speeds just to start showing on the gauge. I thought my gauge was stuck at first. Oil also cools off in traffic and gets warmer at highway speeds or under loads.

What does this mean...This means that's waaaay too cool for oil. Engine oil is the one fluid you do NOT want as cool as you can keep it. Ford definately built an efficient set up that's for sure. I definately wouldn't hurt to do without the water/oil cooler that comes on these. I have a '91 Mustang road race car and I usually see temps around 220 on the street and 235-240 on the track. That's good. If you ask alot of guys at the track or engine builders (even talked to Fluidyne) and they will all tell you oil should be at least 212* Sound familiar? Oil needs to be this warm to keep moisture out of it to prevent sludge and other stuff from building. Everyone I have ever talked to has told me this about oil temps. Fluidyne wouldn't even recommend a cooler until my temps were over 230-250*. I would like to see around 220 (200+ at a minimum) on the gauge on this thing but don't think it's going to happen.

If anyone was thinking about an oil cooler...forget it. If anything, these trucks need an oil heater. With a system that's this efficient, I can't imagine it ever getting even remotely close to requiring a cooler. Not even towing a load in the mountains or anything.

How many oil folks would recommend an oil temp of 220 degree, or recommend a cooler when the oil temps are above 230-250 degrees?

I'm getting ready to respond to this guys post and just want to know your take on it.

Water may boil at 212F, but it evaporates at temps much lower than this. I think that oil temps in the 190F-210F range are ideal ...this way you evaporate the fuel/moisture, without overstressing the oil. My Audi typically runs in this range and my oil analysis results are excellent ...there is never any fuel or water in the analysis.

I'd suggest getting a 195F thermostat in the case you cite ...that should help ....

>>>*There is a lot of controversy over what is proper oil temperature.
When racing, we looked for oil temps in the 220° range as perfection, this was the point of maximum lubrication/power. Anything above 240° was what we called "nerves" territory. We would begin to see failures at much over that point.
For street use, we consider temps in the 160° to 180° as being perfectly normal. Moisture evaporates nicely in those ranges.
I wouldn't be concerned with the temps you are seeing, they seem fine to me....*EB
I measured the oil temp of my Acura RSX by shooting the pan with an IR gun. I get 170 deg F. Your measurements sound about right.
When I look at the big engines from Caterpillar and Waukesha, oil temps run from 80 or so in Waukesha to 90 C in Cat engines. The Cats are more prone to oil oxidation and heat failures. The Waukesha for Nitration, accumulation. Somewhere in there is the right temp for each engine. I think the average person shouldn't fool with what the factory designed. But once we start adding turbos and racing, etc., then cooling has to be added.
When I owned a VW Passat GLX it came with an oil temp gauge as part of the "compuetr display".
I would always set this display to display oil temp (other choices were trip odo, mpg instant, mpg trip etc)

Always watched it as close as I could safely do while driving.

Showed 224F in normal driving in summer.
In cold winter nights (Minnesota) it might stay around 216F-220F when fully warmed up.
when drving hard regardless of season it would go to 230F and stay there until the hard driving would cease (min or two delay).

Alwasy used 15w40 even in MN winter as this was factory recommendation at the time (1994/1995 with a 94 model year car).
Summer oil (dealer recommended) was 20w-50.

i dont have any fancy oil temp gauges, but - I found my cylinder head temp to be within +/- 1-3F from my engine coolant temperature.

With a 180F T-stat (for the chip), my 4.6L SOHC V8 gets to about 205F tops, and after the fan does its job, 180-183F.

I would believe the oil temp to be similar????
I wonder where the oil temperature is measured?? Tust like your coolant/engine temperature the stat sees bulk average temperature when it opens. There are obviously higher water temperatures and lower water temps before the mix. This means that the engine has got to be hotter in some places than even the highest water temp. So obviously the oil which picks up temp as it cools and lubes engine parts will vary. I would think that oil temps would be 20-30 degrees north and south of whatever the gauge says??

So what's my point?? I really don't know.

For some reason, (don't ask me why it's been years since I sourced that) I always thought the oil temp to be about 20F or so above the coolant temp.

With certain engine designs I think one would be surprised at how long it takes a oil to come up to temp at 25 degrees F on the hiway at 60 mph even with a 190 thermostat. At that temp I have drove 15 miles and the oil was hardly warm enough imo to be drained,I did it anyway" thats how I found it was not hot" but then poured the same ambient stored 5/30 into the motor,glug,glug.That was a 74 model Chevy 350 in a 1/2 ton truck,,a 85 Ford 302 gets the oil to temp much faster in winter,,same deal in summer,harder on oil than the other mentioned motor was

Thank goodness for modern oils for guys where it gets pretty darn cold and don't use block heaters

"Anything above 240° was what we called "nerves" territory. We would begin to see failures at much over that point."

Just curious, what type of engine failures/components do you see failing??
Speaking of oil dilema. I bought some Rotella 5W-40 for my son's Cavalier (71,000 miles). I did this because it gets run fairly hard and the thing runs as hot as 220F. When he showed up at my house today. He forgot to bring the Rotella

So I was forced to put in the 5W-30 Shaffer's Molly Pure Syn. Oh well at least I will be able to compare it with 10W-30 Mobil 1 TriSyn (8300 miles on the oil). He its not my car anyway-why should I worry??
Interesting about the 15-20F part...

So that means my 4.6L SOHC V8 oil gets, at the highest temp, to be about 225F.

Is that hot enough?

Originally posted by palmerwmd:

For some reason, (don't ask me why it's been years since I sourced that) I always thought the oil temp to be about 20F or so above the coolant temp.


When I breifly had my 84 Corvette, I watched it's oil temp vs it's coolant temp and found that on a steady highway run they both were pretty much the same, but when stuck in traffic, the oil temp was 15-20F hotter. When first warming up, the oil temp took longer to reach operating temp than the coolant did. I never did watch what the oil temp was under hard driving compared to coolant temp though.
Is it a given that oil temp generally is going to be equal to water temp or no more than about ~20 degree above it? There may be an exception here and there but I'm just looking for a general rule of thumb.

E.g. WaterTemp LT OilTemp LT WaterTemp+20F

If so, does this negate the argument I sometimes here for using heavier oils like 20W50 if you live in the hot desert southwest or other triple digit climates? 20W50 (or 15W50 synth) is a perfectly good oil and there are perfectly good reasons to use it - but I've always wondered about the logic of using it based on external ambient temperatures in a regulated water cooled engine presuming the engine is propertly tuned and cooled for the climate.


NOTE: I had to substitute "LT" for the 'less than' 'equal' symbols I typed. I'm sure there some weird escape sequence characters to allow me to type the character - just not worht the effort to research for 2 silly characters. This bulletin board does not allow me to type in the less than character because it thinks this is HTML (not in this case).

Further when I went 'back' to fix the post and hit the Add Reply button it then informed me that I had to wait 60 seconds as an anti-flooding measure from my previous post. I NEVER SUCCESSFULLY MADE THE PREVIOUS POST! - this is an error in the bulletin board anti-flooding logic - please fix it. Making a simple error and going back and fixing it should NOT constitute triggering the anti-flooding logic.
question? say a oil is 10wt. at 40c.,on start up. - and 30wt.at 100c. one of my trucks runs 170-180deg. water, checked with 2 mech. gages.QUESTION? is----- if oil doe's not reach full temp. 100c. say-- is oil only 20wy. ect. ??? just a thought ....thank's
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