Does conventional Oil cool engines better than Synthetic?


This started at a Harley dealer. I was there to talk to the person who runs the riders education there, I wanted a class for my son so he could get his license. I talked to some sales men and heard this gem from one of them, "A race mechanic told me that conventional oil actually cools an engine better than synthetic. The synthetic oil runs cooler because it does not take as much heat away from the engine as conventional oil. The oil is cooler, but the engine itself is hotter because it doesn't pull the heat from the parts. Of course this is only true for air cooled engines."
Needless to say I was stunned. Could someone really believe this?
Anyway, since I have an air cooled bike I decided to put this to a real test. Now this is not as purely scientific as I would like it to be, but it's the best I could do at the time.
I had originally planned to run both sets of numbers on the same day, but rain on the day I was going to do that prevented that. So instead this happened on consecutive days on my way home from work.

What I did was ride the same route each day home, 12 miles of freeway followed by 9 miles of stop and go traffic. This would have the bike fully up to operating temperature. Then I rode 3.5 miles at 60 MPH with no stops to get a nice even temperature, I then pulled into a parking spot and took temperature readings as quickly as I could.
Then I rode another 2 mile stretch and pulled over, but this time I allowed the bike to idle for 2 minutes before taking my readings to simulate temperatures while sitting at a stop light,
Finally I finished my ride home, stop and go traffic. This is the least controlled part of the ride. But I took temperature reads at home anyway just to ensure the temps had gone down from the stop light simulation.
All temperature readings were taken with the bike shut down to help stabilize the readings. I think any wind blowing would change the temperatures less than if I had left the bike running.

The Testing
 
The test Mule.
My BMW R 1100 S.
OK, Testing starts with the Oil. I used Motorcycle Specific mineral oil. I didn't want the results affected by an oil that was not specific to motorcycles since my regular oil is motorcycle specific. This is the oil they had at my local bike shop, I expect other MC specific oils would have performed the same.
I used this infrared thermometer to take the temperature readings. Not lab quality but it will read consistently with itself so the results will still show if there is any difference between the temperatures the bike runs because of the different oil
I took temperature readings at several spots.
First was in the center of the head. This is the top of the combustion chamber.
I also took readings at the exhaust port and on the barrel where the piston is moving through the bore
I took these readings from both cylinders.
I also took a reading of the oil sump, that would give me the temperature of the oil.

OK, here are the temperature readings from the first run with the mineral oil. On this run winds were light and it was partly cloudy. The stretch of road where I was able to hold my constant speed and take my temperature readings was in the shade of clouds most of the time.

Temperatures with the Mineral Oil
Temperature at the start of the ride88 degrees
Winds at the start of the rideLight
First set of readings, 3.5 miles at 60 MPH
Right Head288.5 Degrees
Right Exhaust279 Degrees
Right Barrel270 Degrees
Left Head279.5 Degrees
Left Exhaust276.3 Degrees
Left Barrel273 Degrees
Oil Sump203 Degrees
Second set of readings, 2 miles at 60 MPH then 2 minute idle.
Right Head300 Degrees
Right Exhaust326 Degrees
Right Barrel292 Degrees
Left Head301 Degrees
Left Exhaust301 Degrees
Left Barrel284 Degrees
Oil Sump222.8 Degrees
Third set of readings, Stop and go to home.
Right Head302 Degrees
Right Exhaust302 Degrees
Right Barrel294 Degrees
Left Head290 Degrees
Left Exhaust296 Degrees
Left Barrel284 Degrees
Oil Sump215 Degrees

Not much change in temperature of the metal from the stop to my house, but the temperature of the oil in the sump did come down. So maybe a little more riding would have seen the metal temperatures coming down too.
Now it's time to change the oil and get my second set of readings

Now on to my normal oil. What can I say, I'm an Amsoil salesman. Although I'm sure other synthetic oils would work similarly.

On the next day, I took the exact same route and ran the same speeds, took the same rest at 2 minutes. The only thing I couldn't control was the traffic to my house after the stop light simulation. It was a little warmer, but not bad. Still Partly cloudy, and the 3.5 miles to the first readings was in the shade of clouds like the previous day.

Temperatures with the Synthetic Oil
Temperature at the start of the ride93 degrees
Winds at the start of the rideLight
First set of readings, 3.5 miles at 60 MPH
Right Head292 Degrees
Right Exhaust301 Degrees
Right Barrel286.7 Degrees
Left Head297.9 Degrees
Left Exhaust285.5 Degrees
Left Barrel266.4 Degrees
Oil Sump215.3 Degrees
Second set of readings, 2 miles at 60 MPH then 2 minute idle.
Right Head312.2 Degrees
Right Exhaust323.6 Degrees
Right Barrel300.0 Degrees
Left Head304.1 Degrees
Left Exhaust306.5 Degrees
Left Barrel296 Degrees
Oil Sump227.3 Degrees
Third set of readings, Stop and go to home.
Right Head302.3 Degrees
Right Exhaust311.9 Degrees
Right Barrel289.7 Degrees
Left Head299.3 Degrees
Left Exhaust292.1 Degrees
Left Barrel291.2 Degrees
Oil Sump233 Degrees

Temperatures with the Mineral Oil
Temperatures with the Synthetic Oil
Temperature at the start of the ride88 degreesTemperature at the start of the ride93 degrees
Winds at the start of the rideLightWinds at the start of the rideLight
First set of readings, 3.5 miles at 60 MPH
First set of readings, 3.5 miles at 60 MPH
Right Head288.5 DegreesRight Head292 Degrees
Right Exhaust279 DegreesRight Exhaust301 Degrees
Right Barrel270 DegreesRight Barrel286.7 Degrees
Left Head279.5 DegreesLeft Head297.9 Degrees
Left Exhaust276.3 DegreesLeft Exhaust285.5 Degrees
Left Barrel273 DegreesLeft Barrel266.4 Degrees
Oil Sump203 DegreesOil Sump215.3 Degrees
Second set of readings, 2 miles at 60 MPH then 2 minute idle.
Second set of readings, 2 miles at 60 MPH then 2 minute idle.
Right Head300 DegreesRight Head312.2 Degrees
Right Exhaust326 DegreesRight Exhaust323.6 Degrees
Right Barrel292 DegreesRight Barrel300.0 Degrees
Left Head301 DegreesLeft Head304.1 Degrees
Left Exhaust301 DegreesLeft Exhaust306.5 Degrees
Left Barrel284 DegreesLeft Barrel296 Degrees
Oil Sump222.8 DegreesOil Sump227.3 Degrees
Third set of readings, Stop and go to home.
Third set of readings, Stop and go to home.
Right Head302 DegreesRight Head302.3 Degrees
Right Exhaust302 DegreesRight Exhaust311.9 Degrees
Right Barrel294 DegreesRight Barrel289.7 Degrees
Left Head290 DegreesLeft Head299.3 Degrees
Left Exhaust296 DegreesLeft Exhaust292.1 Degrees
Left Barrel284 DegreesLeft Barrel291.2 Degrees
Oil Sump215 DegreesOil Sump233 Degrees

Results

Overall the temperatures are a little higher with the synthetic oil but both metal temperatures and the oil temperature. I think this can be due to the higher outside temperature.
I believe the differences are statistically insignificant. Also The oil was not cooler as the, I'll call it an "Urban Legand" stated. So I see no elevated temperatures in the metal that can be attributed to the fact that the synthetis oil did not take away the heat. It is also clear that the synthetic oil is hotter, again counter to the "Urban Legand".
So I believe, as stated before, the differences can be simply attributed to the higher ambient temperature.

The other point here, for this "Urban Legand" to be true. The "Specific heat" of the oils would have to be different. In a basic description specific heat is a measure of a substances (Liquid, solid, gas) ability to absorb heat. This article in Wikipedia discusses the topic
So again, the oils would have to be a very different make up for the conventional oil to carry away more heat than the synthetic. And that is not the case.

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