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2018 dodge ram 2500 6.45L oil running hot

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roland9000

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I have a 2018 DODGE RAM 2500 TRADESMEN 6.4L HEMI.
I swapped out the thermostat /housing and now my oil temps are going thru the roof. Oil Temp keeps on climbing. Coolant temps are perfect. no leaks
Any suggestions as to what is wrong??
 
What temps are you seeing? Maybe we can start a comparison list here. On flat roads, my oil temp is usually within a few degrees of the coolant temp.

Are you seeing this on flat roads or some other scenario? Like towing up hills, etc.

Has the oil been changed regularly? Wondering if you have some kind of reduction in flow.

What's the condition of the radiators on the front of the truck?

Just some ideas I'd look into.
 
motorhead426 said:
What temps are you seeing? Maybe we can start a comparison list here. On flat roads, my oil temp is usually within a few degrees of the coolant temp.

Are you seeing this on flat roads or some other scenario? Like towing up hills, etc.

Has the oil been changed regularly? Wondering if you have some kind of reduction in flow.

What's the condition of the radiators on the front of the truck?

Just some ideas I'd look into.
Click to expand...
Hello,
I'm seeing running temps of 230*. I recently changed the thermostat so I know that might affect it. this is normal driving. not towing and zero hills. I am going to change the oil this weekend.
after looking into it, i guess these temps are not that high, but are higher than before the thermostat change. rad's are in good condition. I just didn't want to over heat the oil and fcck up the engine
 
I saw consistent 230 oil temp this past weekend pulling the 5er. I just changed the oil with PUP and running the Wix filter. I figured this to be normal, especially towing/working a bit.

2021 6.4L @ 38k miles
 
What brand/temp thermostat did you go with?

I am not sure how the thermostat would have that big an impact on oil temps as the oil cooler/heater core get full flow regardless of the thermostat being open or closed.

I am fighting high oil temps as well. I believe I've narrowed my issue down to the oil cooler, but am open to other ideas.

AH64ID

Thread 'High Oil Temps —- Oil Cooler??'

Was Towing with my ‘17 6.4 today and my oil got hot, real hot, twice. I hit 280° on two separate grades, one at 87° ambient and the other at 105°. I was running just over 18K GCW. When the oil hit 280° the rpms were limited to ~4200.

Normal cruising on flat ground, same 18K GCW, coolant is ~204° and oil is ~245°. Highest coolant temp I saw all day was 222° but generally much cooler than that.

I even had a P1521, incorrect engine oil type, active after the first bump of 280° but not the second. It didn’t light the CEL but was active when I scanned. No dash warnings at all.

So I’m...
  • Like
 
AH64ID said:
What brand/temp thermostat did you go with?

I am not sure how the thermostat would have that big an impact on oil temps as the oil cooler/heater core get full flow regardless of the thermostat being open or closed.

I am fighting high oil temps as well. I believe I've narrowed my issue down to the oil cooler, but am open to other ideas.

AH64ID

Thread 'High Oil Temps —- Oil Cooler??'

Was Towing with my ‘17 6.4 today and my oil got hot, real hot, twice. I hit 280° on two separate grades, one at 87° ambient and the other at 105°. I was running just over 18K GCW. When the oil hit 280° the rpms were limited to ~4200.

Normal cruising on flat ground, same 18K GCW, coolant is ~204° and oil is ~245°. Highest coolant temp I saw all day was 222° but generally much cooler than that.

I even had a P1521, incorrect engine oil type, active after the first bump of 280° but not the second. It didn’t light the CEL but was active when I scanned. No dash warnings at all.

So I’m...
  • Like
Click to expand...
Definitely sounds like an external oil cooler is in your future. I've never seen 280 degree oil in a truck before.
 
motorhead426 said:
Definitely sounds like an external oil cooler is in your future. I've never seen 280 degree oil in a truck before.
Click to expand...

Why an external oil cooler instead of fixing what’s not working correctly? Seems counterintuitive.
 
AH64ID said:
Why an external oil cooler instead of fixing what’s not working correctly? Seems counterintuitive.
Click to expand...
"I am fighting high oil temps as well. I believe I've narrowed my issue down to the oil cooler, but am open to other ideas."

It sounded like you figured it was the cooler anyway. I've seen some TFL videos on their "Toaster" test that really cooked the oil and it sounded like your high temp was linked to driving up grades. Just seems like a larger cooler would fix that?
 
motorhead426 said:
"I am fighting high oil temps as well. I believe I've narrowed my issue down to the oil cooler, but am open to other ideas."

It sounded like you figured it was the cooler anyway. I've seen some TFL videos on their "Toaster" test that really cooked the oil and it sounded like your high temp was linked to driving up grades. Just seems like a larger cooler would fix that?
Click to expand...

Sure open to ideas on how to identify and fix it, not on how to bandaid it.

These motors aren’t known for the increased temps I’m seeing, so it’s not a design issue. I have a component not working as designed and hoping to fix that. So I’m open to any thoughts about what’s not working correctly.

I have narrowed it down with my latest oil cooler back flush, but still open. I’m likely not the first person to deal with it. I also suspect lots of people wouldn’t know high oil temps if they had them.
 
roland9000 said:
I have a 2018 DODGE RAM 2500 TRADESMEN 6.4L HEMI.
I swapped out the thermostat /housing and now my oil temps are going thru the roof. Oil Temp keeps on climbing. Coolant temps are perfect. no leaks
Any suggestions as to what is
Click to expand...
Since this happened right after the t-stat there might be an air pocket in the cooling system. Does the 6.4 have a coolant oil cooler/warmer like the 5.7 at the filter housing?
 
Scram said:
Since this happened right after the t-stat there might be an air pocket in the cooling system. Does the 6.4 have a coolant oil cooler/warmer like the 5.7 at the filter housing?
Click to expand...

It does, and it's inline with the heater core which can be a PITA to bleed.
 
Here are some temps I recorded recently driving my 2024 6.4L Big Horn in AZ hauling the RV trailer to a campsite:

9/11/25 93 deg at Payson AZ, el 4890 ft.:
Mixed grades, generally 6%
60 mph on cruise control
Coolant 223 deg
Trans 168 deg
Oil temp 221 deg
Oil pressure 53 psi
 
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