Motor Oils Cool Your Engine

[DGXR]

Yes oil flow is critical to the internal oil cooling process. So thinner oils *can* cool better than thicker oils, which is the main reason why I am not a fan of going too thick (a little is ok IMO). But oil flow is not determined by viscosity alone... the type of oil pump, deposits & sludge, etc. all have an effect on oil flow.

In some cases the figure is 100%

No engine has 100% cooling provided by the circulation of engine oil. Every engine has either a liquid or air cooling design. Liquid cooled engines usually have some air cooling as well.

 

[Loobit]

I'm fine with a thinner oil as long as it has the body to hold up. I would use a Redline or Amsoil 5w20 in a Arizona or New Mexico summertime over a standard Grp3 5w20 hands down. We see a lot of recommended oil weight that are higher for the same engine in other regions so I am open to going up a weight from oe if the temperature,driving style and miles on equipment warrant it. In my own application I have ran one of the thickest 0w20 oils know to be as thick as some 5w30 so Im confident that there is some wiggle room.

I drove from Tucson to Phoenix and back yesterday in a Grand Cherokee Hemi. I put 5w-20 Synthetic in (Royal Purple API). I mixed in a quart of 5w-30 HMX too, so it's a tad thicker. Oil temp the whole time was 215 degrees going 80 and getting a little crazy with the throttle a few times. This was when it was only 90 degrees. It was pretty cool this week.

 

[nascarnation]

Ask any air cooled VW enthusiast about the oil cooling the engine. It does nearly has much as the fan does

Back in the day, on really hot afternoons, it was fairly common to see dead VWs and Corvairs off on the side of the interstate.

 

[spasm3]

Back in the day, on really hot afternoons, it was fairly common to see dead VWs and Corvairs off on the side of the interstate.

I don't know about the bugs. But I had a 914-4. 1.8 L-Jetronic air cooled.
It would vapor lock the fuel line in really hot weather if you stopped moving, like stop and go traffic.

 

[nascarnation]

Don't know if it was vapor lock or something serious, but I saw a good number of them. I'm guessing most of the ones that had a major failure either had a broken/slipping fan belt or were low on oil to start with.

 

[ABN_CBT_ENGR]

I have had this discussion/argument over decades with mechanics and car enthusiasts.
What I learned, many years ago, in Cat Engine diesel school was an oils properties (in order):
1. Cool engine parts
2. Lubricate
3. Keep the engine clean and free of contaminates
We were taught the same when I was trained on the F-16 in the Air Force.

Respectfully they have it backwards then

The first and most distinguishing characteristic of any oil in any tribology regime is to reduce the COF of bodies in motion (lubricate)

Then comes heat transfer ( cooling)

Then washing/cleaning

Sadly, there is a large body of trade literature out there that teaches this also because the term "cooling" is often misleading and misused.

 

[Barry-Oil]

In some cases the figure is 100%

I was not aware of 100% oil cooled.

 

[ABN_CBT_ENGR]

I was not aware of 100% oil cooled.

There's not

 

[Barry-Oil]

Post #18, that pic = engineering fail. So the very hot exhaust heats the fluid going into the cooler, and then heats it again coming out of the cooler? A simple 2cent fiberglass insulating sleeve in that area would remedy that fail.

 

[ABN_CBT_ENGR]

Post #18, that pic = engineering fail. So the very hot exhaust heats the fluid going into the cooler, and then heats it again coming out of the cooler? A simple 2cent fiberglass insulating sleeve in that area would remedy that fail.

Unnecessary and its not a fail of any description.

Air is one of the worst conductors of heat and the small surface area in proximity combined with the fluid velocity would make any thermal transfer negligible at best

 

[ammolab]

My 2011 BMR R1200R MC was described as air/oil cooled. Much oil is directed to the area of the head around the exhaust valve to remove heat. Works I guess, but a water cooled engine soon followed.

 

[ammolab]

Unnecessary and its not a fail of any description.

Air is one of the worst conductors of heat and the small surface area in proximity combined with the fluid velocity would make any thermal transfer negligible at best

Moving air at that!

 

[kschachn]

Moving air at that!

Moving air provides more mass transport for the heat.

 

[ZeeOSix]

What I learned, many years ago, in Cat Engine diesel school was an oils properties (in order):
1. Cool engine parts
2. Lubricate
3. Keep the engine clean and free of contaminates
We were taught the same when I was trained on the F-16 in the Air Force.

I'll take lubrication before cooling. Without adequate lubrication there won't be any running engine to keep cool. Engines can still operate with poor cooling.

 

[ZeeOSix]

Yes.

Let's look at a 5w-20 and 5w-40 as a comparison.

Mobil Super 5w-20 has the following properties:
Visc @ 40C: 47cP
Visc @ 100C: 8.3cP

Mobil 1 Formula M 5w-40 has the following properties:
Visc @ 40C: 79cP
Visc @ 100C: 13.2cP

Let's assume a typical start-up temp of 20C.

At 20C:
5w-20: 118cP
5w-40: 200cP

A difference of 82cP

At 100C our difference is only 4.9cP

At 80C our 5w-20 is the same viscosity as our 5w-40 at 100C.

At a higher oil temp, the difference gets even smaller.

At 120C:
5w-20: 5.7cP
5w-40: 8.9cP
Delta: 3.2cP

Of note, at 120C our 5w-40 is now roughly the same visc as our 5w-20 at 100C.

Those deltas at 100-120C are still enough to make a difference in lubrication protection - ie, MOFT and HTHS.

 

[ZeeOSix]

Yes oil flow is critical to the internal oil cooling process. So thinner oils *can* cool better than thicker oils, which is the main reason why I am not a fan of going too thick (a little is ok IMO). But oil flow is not determined by viscosity alone... the type of oil pump, deposits & sludge, etc. all have an effect on oil flow.

A healthy positive displacement oil pump gives the same volumetric flow regardless of viscosity. So you really aren't getting "more flow and more cooling" with a thinner oil viscosity.

 

[OVERKILL]

Those deltas at 100-120C are still enough to make a difference in lubrication protection - ie, MOFT and HTHS.

Yes, but not flow, which was the point being addressed.

 

[ZeeOSix]

Yes, but not flow, which was the point being addressed.

Positive displacement oil pump has that covered, even with cold oil. Only wrinkle is flow of oil (cold or hot) that is not being forced through the oiling system by the oil pump. Agreed, non-pumped oil flying around inside an engine is basically the same regardless of viscosity when the oil is hot.

 

[Barry-Oil]

Unnecessary and its not a fail of any description.

Air is one of the worst conductors of heat and the small surface area in proximity combined with the fluid velocity would make any thermal transfer negligible at best

Well, there are 30 others worse than air. 31 out of 289 does still make air more of a insulator than conductor, at least from this list.

Solids, Liquids and Gases - Thermal Conductivities

Thermal conductivity coefficients for insulation materials, aluminum, asphalt, brass, copper, steel, gases and more.

www.engineeringtoolbox.com

I am though rather certain the heat coming off those pipes at near 400F is heating those metal cooler tubes, and the oil inside, especially at a stop light.

Point being though, 40% of ALL motor cooling is via the oil. Well, up to 40% I presume. Some here seemed to not know that.

 

[ABN_CBT_ENGR]

Well, there are 30 others worse than air. 31 out of 289 does still make air more of a insulator than conductor, at least from this list.

Solids, Liquids and Gases - Thermal Conductivities

Thermal conductivity coefficients for insulation materials, aluminum, asphalt, brass, copper, steel, gases and more.

www.engineeringtoolbox.com

I am though rather certain the heat coming off those pipes at near 400F is heating those metal cooler tubes, and the oil inside, especially at a stop light.

Your "certainty" is in error for the reasons I already stated.

That tube will never see but a fraction of that heat to start with then being the "cooler"- it will absorb and sink what it does absorb long before it transfers it to the contents. ( that's not even counting any fluid properties, specific heat, transfer coefficient of time or anything else)

The difference is I am an Engineer who does a good bit of heat exchange work in industry and don't need to link hunt to make my point without fully understanding the science represented in the link.