3.6 l Engine Oil Type

[DanW]

Stupid BS Lab shook my confidence in PUP 0w20. Afrer 2000 miles its viscosity was 7.5, and that is a lie. Bdcause virgin it is 8.8

It can easily drop to that, which really is not unusual and is still in grade. The thing to watch for is if it starts thickening. That is the indicator of oxidation which would indicate that the oil needs to be changed. Also remember that oils will almost always differ from their published viscosity just by normal variation in the blending process. So it may have started out below the 8.8 published viscosity, unless you had the actual sample analyzed.

But the only way to be 100% sure of what is happening is to do a VOA from a sample from what you put in and then do a UOA after whatever mileage target you set. That is an expensive way to do it, but you´ll know if there is any shearing or thickening.

One more thing...fuel dilution can cause some slight thinning, too. That´s usually not a major issue with a non-DI engine, particularly the Pentastar. It would be more likely with a great deal of very short trips where the engine doesn´t get up to full temp long enough or if there is a great deal of idling.

I would love to see a UOA from a police car with a Pentastar that idles most of the time. Both virgin and post-change UOA with about 5k or 8k or whatever they run it. We had an officer where I work that had a 3.6 in a Charger police car that idled it all the time....in fact most of the time it was running. They do 5k oil changes. That car had about 200k miles on it and ran fine when they auctioned it off. He never had an engine-related problem with that car. I imagine that´s about as abusive as it can get, with the exception of a granny driving it 1 mile to church or the grocery every day. I would love to see pre/post UOAs for that, too.

A note: The friend who was on the Gen 1 Pentastar design team told me that this engine does better when run hard, as in frequent high rpm running. He said they discovered in long term testing that if you drove like a granny (they called it granny cycling) long enough, the oil in the valve stems would evaporate and cause significant wear. He said hammering it now and then splashes fresh oil back up into the valve stems. They developed a test on the dyno to confirm their findings. He did say you´d have to drive it like a granny for a long time for that to happen, but it was interesting nonetheless. So punch that Pentastar when you feel like it. It´s good for it!

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[roaniecowpony]

I'm at almost 2000 miles on this oil, with over a 1/4 of that on really dusty trails, mostly behind another jeep, eating their dust. I'm changing it today since the Fram Ultra filters and M1 Supercar showed up last night. I'll also pull the air filter and see what's in there as well as the cabin filter. It wouldn't surprise me to find a pile of dirt in the bottom of the air filter box.

 

[Jeep Junkie]

I'm at almost 2000 miles on this oil, with over a 1/4 of that on really dusty trails, mostly behind another jeep, eating their dust. I'm changing it today since the Fram Ultra filters and M1 Supercar showed up last night. I'll also pull the air filter and see what's in there as well as the cabin filter. It wouldn't surprise me to find a pile of dirt in the bottom of the air filter box.

You will use Mobil 1 Super Car 0w40 this time? That's like 14 thick at 100 degrees, almost double than Chrysler MS-6395 0w20🫣

 

[Jeep Junkie]

It can easily drop to that, which really is not unusual and is still in grade. The thing to watch for is if it starts thickening. That is the indicator of oxidation which would indicate that the oil needs to be changed. Also remember that oils will almost always differ from their published viscosity just by normal variation in the blending process. So it may have started out below the 8.8 published viscosity, unless you had the actual sample analyzed.

But the only way to be 100% sure of what is happening is to do a VOA from a sample from what you put in and then do a UOA after whatever mileage target you set. That is an expensive way to do it, but you´ll know if there is any shearing or thickening.

One more thing...fuel dilution can cause some slight thinning, too. That´s usually not a major issue with a non-DI engine, particularly the Pentastar. It would be more likely with a great deal of very short trips where the engine doesn´t get up to full temp long enough or if there is a great deal of idling.

I would love to see a UOA from a police car with a Pentastar that idles most of the time. Both virgin and post-change UOA with about 5k or 8k or whatever they run it. We had an officer where I work that had a 3.6 in a Charger police car that idled it all the time....in fact most of the time it was running. They do 5k oil changes. That car had about 200k miles on it and ran fine when they auctioned it off. He never had an engine-related problem with that car. I imagine that´s about as abusive as it can get, with the exception of a granny driving it 1 mile to church or the grocery every day. I would love to see pre/post UOAs for that, too.

A note: The friend who was on the Gen 1 Pentastar design team told me that this engine does better when run hard, as in frequent high rpm running. He said they discovered in long term testing that if you drove like a granny (they called it granny cycling) long enough, the oil in the valve stems would evaporate and cause significant wear. He said hammering it now and then splashes fresh oil back up into the valve stems. They developed a test on the dyno to confirm their findings. He did say you´d have to drive it like a granny for a long time for that to happen, but it was interesting nonetheless. So punch that Pentastar when you feel like it. It´s good for it!

Hey, if its their best, how come they are giving it away like that?

 

[Jeep Junkie]

Real quick, if oil A flows faster than oil B at -40°, does it mean that oil A will also flow faster than oil B at 40°?

 

[roaniecowpony]

You will use Mobil 1 Super Car 0w40 this time? That's like 14 thick at 100 degrees, almost double than Chrysler MS-6395 0w20🫣

That's exactly what I want when it's 100F and I'm driving around or wheeling in the southwest summer where oil temps can easily hit 245F

 

[Jeep Junkie]

That's exactly what I want when it's 100F and I'm driving around or wheeling in the southwest summer where oil temps can easily hit 245F

Can you not lower the oil temp with the fan through the Tazer? Last week my coolant and oil temp creeped upto 228 degrees. The fan got the coolant down to 185 degrees in a minute and then coolant sucked the heat out of the oil and oil temp got down to 190s as well. I use my Tazer many times during wheeling. But I am not sure how it will do when outside temp is a fiery 100 degrees. I guess I will get to know that in July. Eastern WA does get to 100+ degrees.
Your oil temp in 245 degrees is pretty scary when we have so much plastic in our engine bay.

 

[Jeep Junkie]

That's exactly what I want when it's 100F and I'm driving around or wheeling in the southwest summer where oil temps can easily hit 245F

I read somewhere(Can't find it now) that early 3.6 had issues in its head because 5w30 wasn't moving fast enough to cool things down, so FCA immediately switched to 5w20 the following year. I read on BITOG that thinner oils, though can absorb less heat, can move faster and overall do a better job at cooling. Thicker oils absorb more heat but they move slower and loser heat slower so overall don't do a good job of cooling. Do you agree with this? My experience with 12.2 thick HPL Super Car 0w30 was that it took like 15 minutes longer to completely get to the oil pan for me to get a complete reading on the dipstick, compared to PUP 0w20.. That freaked me out and I changed it immediately. With PUP 5w30 I didn't notice any difference. That HPL oil was crazy thick.

 

[roaniecowpony]

I read somewhere that women are from Venus and men are from Mars. But i have coolant in my engine instead of cooling it with oil. My 0w40 Amsoil has been staying in the main oil galley longer than thinner oil, so a long stop- start event still has oil in the upper end of the engine. Not that I allow ESS to function.
Ymmv.

My Jeep has a highly modified cooling system. The grill is more open than OEM, the transmission cooler is larger, the radiator is larger, the fan is larger and more powerful, and the fan controller has a much lower temperature operating schedule as well as a manual override. The only OEM parts in my coolant system are the water pump and the thermostat.

Since the OEM oil cooler relies on the coolant to moderate oil temperature in a fluid to fluid heat exchanger, which has a higher efficiency than air to oil heat exchangers, keeping the coolant at a lower temperature is very effective at keeping the oil at lower temperatures. My engine coolant temperature runs about 20f lower than the OEM system and stays right at the thermostat rating until an extra load is applied. Then it keeps coolant typically under 205f. Oil temperatures track with the coolant temperature but can have excursions 10-15f higher than coolant with load excursions. Im extremely comfortable with my cooling system as well as the oil cooling temperatures. .

But, your concerns are something you need to consider with your configuration.

 

[roaniecowpony]

JJ,
The whole "thinner oil takes more heat out of the engine thing, or conducts faster, etc, is all small potato stuff.

To put it in perspective, aluminum (as in our cylinder heads and blocks) have a thermal conductivity of about 240 W/m-K. The coolant, is somewhere in the area of 0.43 W/m-K. Generically, oil is around 0.13-0.15 W/m-K. So, coolant is about 3 times more effective at transfering heat than oil, and aluminum is ~1700 times more effective at transferring heat as oil. What this tells us is that the aluminum will get the heat to the coolant (and oiled areas) very effectively. But the coolant will take it away 3 times faster than oil. So, if one oil is a little better at heat transfer than another, it's hardly noticeable in the head or block temperatures. You would achieve more cooling by changing the ratio of ethylene glycol to water in your coolant, since ethylene glycol has a thermal conductivity of about 0.26 vs water's 0.6 W/m-K.

 

[Jeep Junkie]

JJ,
The whole "thinner oil takes more heat out of the engine thing, or conducts faster, etc, is all small potato stuff.

To put it in perspective, aluminum (as in our cylinder heads and blocks) have a thermal conductivity of about 240 W/m-K. The coolant, is somewhere in the area of 0.43 W/m-K. Generically, oil is around 0.13-0.15 W/m-K. So, coolant is about 3 times more effective at transfering heat than oil, and aluminum is ~1700 times more effective at transferring heat as oil. What this tells us is that the aluminum will get the heat to the coolant (and oiled areas) very effectively. But the coolant will take it away 3 times faster than oil. So, if one oil is a little better at heat transfer than another, it's hardly noticeable in the head or block temperatures. You would achieve more cooling by changing the ratio of ethylene glycol to water in your coolant, since ethylene glycol has a thermal conductivity of about 0.26 vs water's 0.6 W/m-K.

I will try ESP 0w30 this summer then

 

[roaniecowpony]

I will try ESP 0w30 this summer then

My current thought is that keeping the oil clean and not allowing varnish to build may be what prevents a lifter issue which fails the rocker/cam. You can do that by keeping OCI short, using an oil with good detergents, and keeping oil temperatures in check.

 

[Jeep Junkie]

My current thought is that keeping the oil clean and not allowing varnish to build may be what prevents a lifter issue which fails the rocker/cam. You can do that by keeping OCI short, using an oil with good detergents, and keeping oil temperatures in check.

PUP makes big claims of keeping things clean.

 

[roaniecowpony]

PUP makes big claims of keeping things clean.

 

[Jeep Junkie]

ESP also has boatloads of sulfur and zinc

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