Oil pressure, temp and viscosity

[digger]

SPECS:

so i have an oil pressure sensor (same location as OEM warning sensor) and an oil temp sensor that is the oil pan drain plug (not ideal). i use a 10W-50 oil and have the stock m20b25 oil cooler and my idle speed is 925rpm. the pressure sensor retains the warning light but at 13psi instead of 7psi as per stock switch (or is it 9psi??)

COLD FIRST THING IN MORNING

in the cold/cool morning at idle and at speed the pressure remains at 70psi

SPRING AFTER WARMUP

on a 20-25C/68-77F sort of day when the engine is fully upto temp at idle the oil temp is apparently around 75C-80 when just been cruising around. the oil pressure would be between 25-30psi thought its hard read accurately

GIVE IT SOME STICK

if i give it some right foot for a period of time the oil temp goes upto 200F (93C) and pressure will drop to between 15-20psi but temps will come back down after just cruising around.

THOUGHTS

based on this id say the oil is too thick as when cold the pressure is way up there even at idle and surely this means the flow is reduced during warmup.
The oil is not getting hot enough under normal conditions and a thinner oil might be more suitable.

i'm looking to try a 10W-40 to see what effect this has, it should be thinner when cold despite still being a 10W and it might suit the temps mine currently sees a bit better.

QUESTIONS

I assume when cold there is a relief valve that regulates this maxima or circa 70psi? is this in the pump or the one that screws into the block inside the pan?

i'm interested in the oil temperature, is there any sort of thermostat that is supposed to be operating? id like to see a bit higher temperature under normal conditions to burn off condensate and reduce dilution.

Does anyone have similar data?

[dnguyen1963]

If the temperature is around 20C, I would prefer 15W40 oil. An IR temp gun is a cheap and accurate way to measure the oil temp.

[TobyB]

Remember, you're measuring at the BOTTOM of the pan, where, in theory, the oil's
cooled the most by the pan.

Yes, there's an oil pressure relief valve- cold, mine holds close to 70,
and hot, 60 is normal

Yes, there's a thermostat in the oil head bolted to the side of the block, where the lines split off to the cooler.

My numbers, from a 160k engine, Mobil1 15-50
<edit- measured in the bottom of the pan as well>
are that oil temps run 190- 200, pressure is limited
at 60, and idle just lets the 20psi light come on sometimes after I've been chasing a train
in hot temps for a lot of laps, when the oil temp can get up to 240.

hth

t

[digger]

If the temperature is around 20C, I would prefer 15W40 oil. An IR temp gun is a cheap and accurate way to measure the oil temp.

How does the viscosity for 15w-40 at say 40f compare to 10w-50 in general? without seeing graphs vs temp i'd guess it be thicker for cold start but maybe only at extremely low temps

[digger]

Remember, you're measuring at the BOTTOM of the pan, where, in theory, the oil's
cooled the most by the pan.

Yes, there's an oil pressure relief valve- cold, mine holds close to 70,
and hot, 60 is normal

Yes, there's a thermostat in the oil head bolted to the side of the block, where the lines split off to the cooler.

My numbers, from a 160k engine, are that oil temps run 190- 200, pressure is limited
at 60, and idle just lets the 20psi light come on sometimes after I've been chasing a train
in hot temps for a lot of laps, when the temp can get up to 240.

hth

t

Yes the pan is not ideal are your numbers taken in the pan? Maybe someone has measured the pan and somewhere a little better and can give some correlations....

[reelizmpro]

I have both temp sensors in the pan and oil filter housing in the oil flow. The pan temp was cooler by 15 degrees or so.

[digger]

I have both temp sensors in the pan and oil filter housing in the oil flow. The pan temp was cooler by 15 degrees or so.

C or F?

[reelizmpro]

Fahrenheit

[george graves]

An IR temp gun is a cheap and accurate way to measure the oil temp.

I'm not a fan of those IR guns. Especially on reflective surfaces - it throws them off.

[dnguyen1963]

I'm not a fan of those IR guns. Especially on reflective surfaces - it throws them off.

I have never taken measurement at only one location. It is so quick so you can measure all over the engine and take an average.

[dnguyen1963]

How does the viscosity for 15w-40 at say 40f compare to 10w-50 in general? without seeing graphs vs temp i'd guess it be thicker for cold start but maybe only at extremely low temps

Hope this helps.

http://www.elephantracing.com/images/techtopic/oiltemperature/viscosityvstemperature400.gif

[digger]

Hope this helps.

http://www.elephantracing.com/images...erature400.gif

found this to

http://www.viscopedia.com/viscosity-tables/substances/engine-oil/

based on this id say that at 20C 15w-40 has approx same viscosity as 10w-50

10w-40 seems better as from 50C up its the same as 15-40 but its gonna flow more below 50C, that and i can get the same type of oil as i use now in 10w-40...when it starts getting really hot here the 10w-50 might still be the go

[TobyB]

I also tried running sensors in the engine- the problem with anything metal- mounted
is that the conduction heating/cooling of the sensor is significant. I even stuck one in
an AN fitting in front of the radiator- and it ran noticeably cooler (15 deg f, ish)
than when I ran the same assembly BEHIND the radiator.

Currently, I run an 'extended' Autometer sensor with the bulb as high in the
pan as was easy to do without killing myself... and really only worry about
relative temps, as in, "If the oil's not warm, don't flog it yet"

t

[digger]

I also tried running sensors in the engine- the problem with anything metal- mounted
is that the conduction heating/cooling of the sensor is significant. I even stuck one in
an AN fitting in front of the radiator- and it ran noticeably cooler (15 deg f, ish)
than when I ran the same assembly BEHIND the radiator.

Currently, I run an 'extended' Autometer sensor with the bulb as high in the
pan as was easy to do without killing myself... and really only worry about
relative temps, as in, "If the oil's not warm, don't flog it yet"

t

that is an excellent point, about the sensor being heat due to conduction and radiation affecting the temperature. this also applies to the IAT. i feel the absolute temps also matter as you want to keep the oil hot to get rid of contaminants. that's why lots of short trips are hard on an engine

[digger]

So I’ve changed over to 10W-40 and the pressures are still good and temps are basically the same. Even on a 30C day with 85-90C oil temp the pressures are still over 20psi at idle.