Oil temperature vs water temp

I have a question regarding engine oil temp compared to water temp on my HD16.  What should the temperature difference be between the two?  When the engine is cold the oil pressure is great, about 55-60 lbs, after warming up im only maintaining about 35-40 lbs which is borderline low.  I feel like the oil is getting too hot. 

Just due to friction and pressure engine oil can get to 240-260 degrees F 115-126 C, cooling only is designed to keep it around there and to keep cooler oil fed to a turbocharger.  Most likely you are not seeing a heated oil issue more than internal engine wear, when tolerances open up the oil pump relief can pretty well compensate during cold operation but not so much so when the engine does reach operating temps, the valve just goes closed and the wear drops the oil pressure.  Combination of gear wear in oil pump, cam bearings, main and rod bearings, rocker shaft wear, all add up to line loss.

If you get much more than 250 degrees, you are gonna scorch the oil.  I would suggest you buy a cheap IR thermometer, and start checking different spots on the motor, to see the actual temps you are guessing at now.  HF has the IR thermometers from $29.99, saw one at lowe's for $35.

cenex superlube TMS 15-40

Steve in NJ wrote: I don't know what the OP specs are supposed to be in an HD16, but its a fact as engine oil gets hotter, it thins out. Add in engine wear on the mains & the oil pump system, and OP drops even more. To me, 35-40 lbs of OP doesn't sound bad after the engine is up to temp, but as I mentioned, I don't know what the spec's are. If it holds rock solid at 35-40 lbs, and the engine is quiet, I wouldn't worry bout' it. We have a few pieces of heavy equipment here at work that have quite a few hours on em' and they run around the same in OP. As D Miller said, its a matter of wear.... Steve@B&B

but its a fact as engine oil gets hotter, it thins out.

not true it may flow better out of the base plug
when it hot but it not thinner

if a motor oil passes the cold temperature or
W (winter grade) specification for a SAE 15W
and at 210° F (100° C) flows through the viscometer
like a SAE 40 motor oil, then the label will read
15W-40. Get the picture? Consequently, if the motor
oil performs like a SAE 5 motor oil on the reduced
temperature scale and flows like a SAE 20 at 210° F
(100° C), then this motor oil's label will read 5W-20.
And so forth and so on!

 say that they wouldn't use a 5W-30 motor oil because it is,

"Too thin." Then they may use a 10W-30 or SAE 30 motor oil.

At engine operating temperatures these oils are the same.

The only time the 5W-30 oil is "thin" is at cold start up

conditions where you need it to be "thin."

So how do they get a motor oil to flow in the cold

when it is a thicker viscosity at 210° F?
The addition of Pour Point Depressant additives (VI) keep the paraffin in petroleum base oils from coalescing together when temperature drops. Pour Point Depressants can keep an oil fluid in extreme cold temperatures, such as in the arctic regions. 

To me, anything over 15- lbs of OP doesn't sound bad

after the engine is up to temp we would all like to see 

more up to 65 lbs  but the engine will get all the lube

it need at 15 lbs 

IMHO     B:-)      Dnoym

i've never heard of many diesel engines that require high levels of op when hot. 35-40 hot sounds like plenty of op to me and having 60 or so when cold, nothing sounds out of line to me. what does the manufactures specs say?

855 Cummins engines have clocked over 20,000 hours in trucks with pressure down around 30 pound for the last 10,000 or so trouble free. At 30 pound the flow or volume of oil is still keeping the crank and heavily loaded cam happy in those pressure/time engines