Oil pressure & weather conditions

[3406E]

Cm870- with the hot weather my oil psi went down to 28-29 today.It usually runs at 31-33 @1400-1500 rpm going down the road.Had to pull in a truck stop and cool off also added a quart of gear oil. It went back to normal but after about 3 hours of driving I was back to 29.The humidity of the weather went up to almost 100 degrees today. Sadly I wasnt paying attention to my oil temp .I’m just at 8k on this oil. Rotella T6 full syn. Anytime it does this it does not change the idle psi which is at 20-21 always. This is not the first time this happened last year summer in Miami and Houston which as you know are very hot place. I usually just change the oil when this happens but I don’t want to keep doing it wasting money. I change my oil every 12k.Im almost at a million millions miles ; should be getting it rebuilt in no longer than a month or two the most. I also planned to get a new oil pump when rebuilding.My buddy runs a couple cm871 in dump trucks and he said he seen his go down 20-25 lol when it’s really hot,his exact Words were “it’s not a cat ”and he runs them like that. I wouldn’t dear try with mine though. What are your thoughts with hot weather and oil psi?have anyone experienced this? How much of a drop in pressure is aceptable or is it aceptable at all?

[3406E]

And to add my fan stayed on all day only cut out when the sun went behind the cloud as i was headed west straight towards it

[hhow55]

I never the problem you describe, being i used conventional oil with a gallon of gear lube for my truck. And btw it was a cm871.

[hhow55]

(06-24-2025 )3406E Wrote:  And to add my fan stayed on all day only cut out when the sun went behind the cloud as i was headed west straight towards it

Sounds to me you have an engine running hot situation, which certainly can cause lower oil pressure.

[3406E]

Well my water temp was normal and my oil temp didn’t spike or anything. This is an image before i shut it down to cool off

[3406E]

Attached image

[mikkhh]

Why you waste money on synthetic oil?
Mineral Rotella 15w40 will work just fine.

5w40 will break down faster towards base viscosity which is 5w on 5w40 compared to 15w on 15w40 .

https://rawze.com/forums/showthread.php?tid=1913

[Rawze]

first and foremost ... bad deletes can make the oil run hotter than it should, and therefore cause lower than normal oil pressures as a result.

next ... it is very common for oil pressure to drop if the oil is getting too much soot in it. It clogs the oil filter and causes oil pressures to run low. - Changte the oil with fresh oil, and the poressures come back to normal for a few weeks. <-- that is a clkear sign of excfess soot in the oil.

and for reference... 32-34 psi while driving (enigne revved up and at driving speeds) is normal.. anything below about 30-psi when driving is too low, and there is something wrong.

At idle,. anything below about 28 or so is too low, unless oilk is real hot, then anythng below about 18-20 would be until oil cools off.



and.. STOP USING GARBAGE SYNTHETIC OILS unless you have some dammned extreme cold or something to require it. Your wasting your moneys and time completely otherwise.. and causing more harm then good if that syn oi8l is thinner than the recommended 40-wt that the engine calls for.


and.. yeah.. a gallon of gears lube on an older engine that likely has higher than normal bearing clearances is not a bad idea too.

and... if your almost at a million miles.. WHEN IS THE LAST TIME the bottom end was done?. All rod-main bearings replaced?. Its due at 800k miles to prevent wrist pin failure and a piston going thru the block without any warning!.

[3406E]

Nope,unfornately no bearings replacement