Temp Difference with Previous Pentastar

[mwilk012]

Your GC is running too cold. Thermostat shouldn’t open up until 190, and is fully open at 212F.

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[Capricorn]

I own a 2021 2-door JL and a 2016 Grand Cherokee, both with Pentastar engines. However, I quickly noticed that the engine oil temp in the JL is usually about 20 to 30 degrees hotter than the Grand Cherokee under the same driving and environmental conditions. I'm not 100% certain about why this occurs, but I suspect it is because the Pentastar in the Grand Cherokee is the previous version of the engine that requires 6 quarts of oil instead of 5. My theory is that the greater oil capacity dissipates heat better, but just curious what others think and if anyone has noticed differences in engine life/performance as a result. Appreciate the feedback and happy Jeepin' y'all!

JL will always run hotter than GC as it is heavier and way less aerodynamic. Under same driving conditions, the engine in JL has to work much harder, hence more heat.

 

[mwilk012]

JL will always run hotter than GC as it is heavier and way less aerodynamic. Under same driving conditions, the engine in JL has to work much harder, hence more heat.

Yea, if the thermostat wasn't a factor.

 

[Bob Burd]

Extra oil capacity probably adds almost nothing to heat dissipation. It's more controlled by the metal housing and thermal regulation. More oil would make it take longer to reach operating temperature.

 

[flyer92]

JL will always run hotter than GC as it is heavier and way less aerodynamic. Under same driving conditions, the engine in JL has to work much harder, hence more heat.

Perhaps the 4-door JL is heavier than GC, but some quick internet research revealed that the GC's curb weight is 4875 lbs and 2-door JL Sport is 3970 lbs....probably even less without my back seat and with soft top/half doors installed. My JL is therefore 905 lbs lighter than my GC, which is why I was curious about the significant temp difference. Only thing I can think of is that the GC's older Pentastar has greater oil capacity...and of course, the JL is as aerodynamic as a brick.

 

[Yawnie'sPapa]

JL will always run hotter than GC as it is heavier and way less aerodynamic. Under same driving conditions, the engine in JL has to work much harder, hence more heat.

Nope. Heat is removed by the cooling system. They should run the same. In your thinking the built 360 in my Javelin should run hotter than the 4.0 in my SX4, or my JT should run hotter when it's towing than one of my cars. The fact is, the temperature is controlled by the cooling system, period, no matter what engine or how hard it's working. Yes, it will generate more BTUs during use, but the radiator and fan remove the heat and it's regulated by the thermostat and cooling fans to between 190-220 in most cases (normal for my JT and for the Grand Cherokees we've had)
Oil will follow closely but can be 10 to 15 degrees different.
And no, the 5 quarts isn't the reason for the heat difference. It's not removing that much heat from the engine.

The thermostat in normal vehicles determines the minimum operating temperature. The cooling system removes excess heat and controls the top operating temperature. There's a range of operation in these because of how these stats work - and the electronically controlled fans. The fans are regulated not just for heat removal, but for engine load as well (electric fans DO require horsepower because the alternator generates the power to run the fans and at full capacity, one of these alternators can pull around 4 horse power.

There's nothing about the weight or shape of a vehicle causing a difference. If one is running too cold, there's a problem likely with thermostat. If running too hot - there's a stat problem (sticking closed or partially closed) or the fans aren't operating correctly, or there's a restriction in coolant flow, etc.

That's from my college training and tech experience.

 

[Capricorn]

Nope. Heat is removed by the cooling system. They should run the same. In your thinking the built 360 in my Javelin should run hotter than the 4.0 in my SX4, or my JT should run hotter when it's towing than one of my cars. The fact is, the temperature is controlled by the cooling system, period, no matter what engine or how hard it's working. Yes, it will generate more BTUs during use, but the radiator and fan remove the heat and it's regulated by the thermostat and cooling fans to between 190-220 in most cases (normal for my JT and for the Grand Cherokees we've had)
Oil will follow closely but can be 10 to 15 degrees different.
And no, the 5 quarts isn't the reason for the heat difference. It's not removing that much heat from the engine.

The thermostat in normal vehicles determines the minimum operating temperature. The cooling system removes excess heat and controls the top operating temperature. There's a range of operation in these because of how these stats work - and the electronically controlled fans. The fans are regulated not just for heat removal, but for engine load as well (electric fans DO require horsepower because the alternator generates the power to run the fans and at full capacity, one of these alternators can pull around 4 horse power.

There's nothing about the weight or shape of a vehicle causing a difference. If one is running too cold, there's a problem likely with thermostat. If running too hot - there's a stat problem (sticking closed or partially closed) or the fans aren't operating correctly, or there's a restriction in coolant flow, etc.

That's from my college training and tech experience.

I owned two Xtreme Recons and had non XR JL Wranglers with same 3.6L engines and have same cooling system and thermostats. Yet my XRs ran temps 10-15F more than non XRs in the same situations.

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