Strange observations after oil change

[Clevy]

Hey guys
So I changed the oil in my charger yesterday. Last night I was driving into the city(35 miles each way) I wanted to see if there was any pressure and temp differences because I used 5 litres of liqui-moly 0w-40,a quart of pennzoil 0w-20 and a can of cera-tec.
The oil temp previously on a steady highway drive is always 213f,always,regardless of ambient temps outside. I set cruise at 70mph.
Oil pressure at that speed is always 49psi.
Last night oil temp stabilized at 202f,oil pressure was 51psi. I can understand the psi change because the oil is slightly thicker however the oil temp being 10f cooler kinda baffles me.
I'm not concerned about any engine damage or anything I just found it odd that oil temps decreased.
Hot oil pressure with Mobil 1 5w-20 at idle was 19-20psi,now its 21-22 which I don't see as a big deal and pressure at 70mph with cruise on also increased slightly to 51 psi from 49.
Anyone have a theory as to why my oil temps are lower.

Thanks

I expected more of a oil pressure increase going to a 40 grade from a 20 but my gauges show its nominal.

 

[SatinSilver]

How do you know the temperature and psi? Scanguage or something etc...

 

[nitehawk55]

Some synthetics do make the engine run cooler .

 

[hemitom]

Gremlins under the hood with hand held fans. seriously i would think it would be the other way around with oil temps being higher with the 5w40??

 

[Clevy]

Originally Posted By: satinsilver
How do you know the temperature and psi? Scanguage or something etc...


I have the evic option so I've got a digital oil pressure and oil temp readout.

Originally Posted By: nitehawk55
Some synthetics do make the engine run cooler .


I had M1 in before this oil change so they are both synthetics.

Originally Posted By: hemitom
Gremlins under the hood with hand held fans. seriously i would think it would be the other way around with oil temps being higher with the 5w40??



That was my assumption as well. Everything I've read leads me to believe that oil temps should have increased,which is why I posted this thread. I found this whole thing quite odd. Its a 0w-40 though,not 5w-40 not that it should matter.

As far as the whole idea that the mds function the only thing I noticed it the transition from 4 to 8 isn't as noticeable,seems smoother.

Engine isn't as free revving as before too. That was immediately evident.
The reason I went with this grade was because idle times will be increasing and I thought it wise as a counter measure for fuel dilution. And I wanted to start using up this massive amount of stock I've got.
I'll be monitoring the oil condition too. The M1 didn't get dark enough to be visible on the dipstick til around 3500 miles,even with the black mos2 in the oil.
Ceratec is milky but diluted enough its barely affected oil colour.

 

[UNC017]

Originally Posted By: satinsilver
How do you know the temperature and psi? Scanguage or something etc...


Chrysler LX/LC cars allow you to display oil pressure or temp on the Electronic Vehicle Info Center (EVIC) readout in the bottom of the speedometer pod using the steering wheel display controls to select what gets shown. Pretty handy- I leave mine set on oil pressure most of the time and flick it to temp now and then when I get bored. Sometimes I check the tire pressures, too- kinda cool to watch those change in (slow update) real-time as the tires warm up.

As for why the oil temp changed, I suspect its related to flow rate past where the temp sensor is located. Higher vis means lower flow, so the oil gets hotter up in the engine since it stays there longer, but then gets cooler since it stays in the pan longer also. By comparison a thinner oil would flow faster, reach a lower peak temp in the engine but then not cool off quite as much in the pan either. The overall average temp of all the oil in the system would stay the same (just a theory, mind you...) Mine always shows a pretty stable oil temp, but not THAT stable- it ranges from 220F to 235F depending on weather, my driving, etc. with no change in oil at all. Of course mine has an oil cooler (6.4L) and I always run 0w40. There was no discernable temp difference between Pennzoil Ultra 0w40 and Mobil 1 0w40 though.

 

[Clevy]

Originally Posted By: 440Magnum
Originally Posted By: satinsilver
How do you know the temperature and psi? Scanguage or something etc...


Chrysler LX/LC cars allow you to display oil pressure or temp on the Electronic Vehicle Info Center (EVIC) readout in the bottom of the speedometer pod using the steering wheel display controls to select what gets shown. Pretty handy- I leave mine set on oil pressure most of the time and flick it to temp now and then when I get bored. Sometimes I check the tire pressures, too- kinda cool to watch those change in (slow update) real-time as the tires warm up.

As for why the oil temp changed, I suspect its related to flow rate past where the temp sensor is located. Higher vis means lower flow, so the oil gets hotter up in the engine since it stays there longer, but then gets cooler since it stays in the pan longer also. By comparison a thinner oil would flow faster, reach a lower peak temp in the engine but then not cool off quite as much in the pan either. The overall average temp of all the oil in the system would stay the same (just a theory, mind you...) Mine always shows a pretty stable oil temp, but not THAT stable- it ranges from 220F to 235F depending on weather, my driving, etc. with no change in oil at all. Of course mine has an oil cooler (6.4L) and I always run 0w40. There was no discernable temp difference between Pennzoil Ultra 0w40 and Mobil 1 0w40 though.


That theory definitely makes sense.
The only reason I noticed is because of how stable the temps have been since I owned this car.
Oil temp only increases if I'm manually shifting,holding a gear longer and getting the rpm up to 5000.
Ambient temp has never affected my oil temp til now. So I don't think that's the determining factor.
If I'm playing then yeah I've had oil temps up to 260f but even in traffic with lots of stop and go the oil temp never increased past 220f.
I think my next hemi will be a 6.4. It's got mds. I'm spoiled now with that system.
My moms dodge caliber at best gets 32mpg on the highway with high teens in the city. My charger is getting 30mpg on the highway depending on wind conditions and roughly equal,or even better city mileage.
The cylinder deactivation system is a must have for me now. The fuel consumption of a 6er with the on demand power of a hemi.
Life is sweet

 

[OVERKILL]

Originally Posted By: 440Magnum


As for why the oil temp changed, I suspect its related to flow rate past where the temp sensor is located. Higher vis means lower flow, so the oil gets hotter up in the engine since it stays there longer, but then gets cooler since it stays in the pan longer also. By comparison a thinner oil would flow faster, reach a lower peak temp in the engine but then not cool off quite as much in the pan either. The overall average temp of all the oil in the system would stay the same (just a theory, mind you...) Mine always shows a pretty stable oil temp, but not THAT stable- it ranges from 220F to 235F depending on weather, my driving, etc. with no change in oil at all. Of course mine has an oil cooler (6.4L) and I always run 0w40. There was no discernable temp difference between Pennzoil Ultra 0w40 and Mobil 1 0w40 though.


Doesn't this engine have a positive displacement pump? If so, unless it is on the bypass, the flow is the same.

 

[Clevy]

Originally Posted By: OVERKILL
Originally Posted By: 440Magnum


As for why the oil temp changed, I suspect its related to flow rate past where the temp sensor is located. Higher vis means lower flow, so the oil gets hotter up in the engine since it stays there longer, but then gets cooler since it stays in the pan longer also. By comparison a thinner oil would flow faster, reach a lower peak temp in the engine but then not cool off quite as much in the pan either. The overall average temp of all the oil in the system would stay the same (just a theory, mind you...) Mine always shows a pretty stable oil temp, but not THAT stable- it ranges from 220F to 235F depending on weather, my driving, etc. with no change in oil at all. Of course mine has an oil cooler (6.4L) and I always run 0w40. There was no discernable temp difference between Pennzoil Ultra 0w40 and Mobil 1 0w40 though.


Doesn't this engine have a positive displacement pump? If so, unless it is on the bypass, the flow is the same.


I don't know for sure the type of pump. I suspect there is something special going on because even when cold and driving the oil pressure never really spikes and will run at 55psi until hot then drops to the 52psi I see now but 49psi when I had 5w-20 in the sump.

 

[crazyoildude]

I only use oil in my engines and have no problems!
We rebuild hundreds of engines each year and dont usually have problems with them either on just oil and regular bulk oil. we once had someone in a 4 runner with very low miles (i cant remember exactly how many) and the engine was rapping with little to no oil pressure and the guy said he does not know what happened but it happened after he filled his crankcase with 20 bottles of stp oil treatment! I guess he thought if the bottle said 1 pint is good a gallon would be better .. This is a true story you cant make this stuff up!

 

[Clevy]

Originally Posted By: crazyoildude
I only use oil in my engines and have no problems!
We rebuild hundreds of engines each year and dont usually have problems with them either on just oil and regular bulk oil. we once had someone in a 4 runner with very low miles (i cant remember exactly how many) and the engine was rapping with little to no oil pressure and the guy said he does not know what happened but it happened after he filled his crankcase with 20 bottles of stp oil treatment! I guess he thought if the bottle said 1 pint is good a gallon would be better .. This is a true story you cant make this stuff up!



I'm not sure where exactly I said it was a problem. If anything this issue presents a positive since oil pressure has increased slightly and oil temps are lower.
Wouldn't that be considered a positive?
Oil pressures and temps were consistent before and after the addition of mos2 using Mobil 1 5w-20. I switched to 0w-40,with a quart of 0w-20 and a can of cera-tec and something changed,for the better.
I completely expected the pressure increase although I anticipated a bigger jump,the only part of this that I found weird was the oil temp decrease. I expected an increase in oil temps based on what I've learned but that didn't occur.
In any case 440 magnum has presented the best guess so far.
I'm not sure exactly what the quoted post has to do with the thread topic however I guess everyone's got something to say,regardless if its even remotely applicable.
Thanks for sharing

 

[crazyoildude]

my beliefs are to leave the oil mixing to the oil companies we do engines and only engines we go to all the engine rebuilding seminars in the area and i also have taught and one thing i have learned from everywhere that you should not put anything into your oil it changes everything! Just my professional opinion others may argue. as for the stp i wrote about my brother said it was 10 bottles not 20, lol

 

[Challenger71]

Clevy, I dont think the viscosity change has much to do here in your situation. I would attribute more of the temp reduction to the ceratec additive. That nano-ceramic additive is high-speed product and really works as claimed by LM. The friction reduction is a notable candidate related to temp.

 

[jrustles]

Originally Posted By: Challenger71
Clevy, I dont think the viscosity change has much to do here in your situation. I would attribute more of the temp reduction to the ceratec additive. That nano-ceramic additive is high-speed product and really works as claimed by LM. The friction reduction is a notable candidate related to temp.


I'd tend to agree. If Clevys results were substantiated under controlled conditions, it would strongly suggest a reduction of friction/drag due to increased FM.

 

[camelCase]

tl;dr

Newer oil can have better thermal conductivity. This allows it to "dump" its heat into the coolant more effectively if all other conditions are the same.

This could account for the ~10ºF drop in temperature.

 

[Nate1979]

This may be a really stupid idea but is it possible the additive has coated the temp sensor and is affecting the reading?

 

[UNC017]

Originally Posted By: OVERKILL
Originally Posted By: 440Magnum


As for why the oil temp changed, I suspect its related to flow rate past where the temp sensor is located. Higher vis means lower flow, so the oil gets hotter up in the engine since it stays there longer, but then gets cooler since it stays in the pan longer also. By comparison a thinner oil would flow faster, reach a lower peak temp in the engine but then not cool off quite as much in the pan either. The overall average temp of all the oil in the system would stay the same (just a theory, mind you...) Mine always shows a pretty stable oil temp, but not THAT stable- it ranges from 220F to 235F depending on weather, my driving, etc. with no change in oil at all. Of course mine has an oil cooler (6.4L) and I always run 0w40. There was no discernable temp difference between Pennzoil Ultra 0w40 and Mobil 1 0w40 though.


Doesn't this engine have a positive displacement pump? If so, unless it is on the bypass, the flow is the same.


Its my belief that these engines (and Mopars in general) are on the relief valve- not the filter bypass- most of the time. As RPM increases , the pressure will rise quickly to a certain level and then rise very slowly thereafter. When fully hot my 6.4 hits ~55 PSI by about 1500 RPM. At 3500, you *might* see 60-62 PSI. Whatever the case, the "10 psi per 1000 RPM" rule of thumb has NEVER applied to any Mopar of any vintage that I've ever owned. I really think that the designers have always wanted a relatively constant oil pressure. Even my '49 Plymouth flathead six pretty much hit its max oil pressure at around 2x idle RPM.

 

[OVERKILL]

So oil is dumping out the bypass (on the oil pump)/relief valve all the time? that seems a bit nuts, LOL!!! It would be heating/beating the oil up a bit.

Quite the opposite experience with my old Ford engines

EDIT: And yes, I was speaking about the bypass on the pump (relief valve) not on the oil filter

 

[UNC017]

Originally Posted By: OVERKILL
So oil is dumping out the bypass (on the oil pump)/relief valve all the time? that seems a bit nuts, LOL!!! It would be heating/beating the oil up a bit.

Quite the opposite experience with my old Ford engines

EDIT: And yes, I was speaking about the bypass on the pump (relief valve) not on the oil filter

I *definitely* think that is true on older Mopars, just based on gauge behavior. How else can you explain a "knee" in the pressure/RPM curve?

And I agree, the few Fords I had never had a pressure/RPM curve that looked like my Mopars- they look more like Chevies in showing a pretty linear rise with RPM. It wouldn't be the first time that Mopar did something that wasted a fair bit of energy... although you have to remember that since the oil is virtually incompressible, it doesn't represent as much energy as, say, venting compressed air does. But there is definitely some extra load on the pump due to moving a larger volume of oil than necessary up to a higher pressure.

FWIW, they certainly took a different approach with the Pentastar to achieve RPM-independent lubrication. But they eliminated the wasted power of venting pressurized oil out the relief valve by using a variable-displacement pump... and at the same time let the computer control the oil pressure based on various sensor parameters. I've had rental Pentastars where the EVIC indicated pressure dropped at a certain RPM as the engine warmed up. If they provided a conventional gauge on those cars (and didn't make it an 'idiot' gauge) they'd be fielding all sorts of "why is my oil pressure going crazy?!? complaints.

I don't think the Hemis have variable-displacement pumps, but the pressure on mine sure is more constant than almost any other engine (Mopar or otherwise) I've had, once it gets above about 1200 RPM anyway.

 

[Clevy]

Originally Posted By: Nate1979
This may be a really stupid idea but is it possible the additive has coated the temp sensor and is affecting the reading?


I doubt it. Cera-tec can't really coat anything. It needs pressure to force it into the hills and valleys of metal.
And before it comes up the idea crossed my mind that the cera-tec may have contributed to the lower temps however cera-tec needs time to plate,just like mos2 and this temp drop was instantly right after the oil change.
Maybe the liqui-moly 0w-40 isn't absorbing as much engine heat but coolant temps haven't changed.
I just find the oil temp thing odd since I assumed the oil temps would increase based on what I've learned on bitog.
I'm not complaining just found the whole thing odd.