Synthetic oil and engine operating temps

[Lyondellic]

I have used Amsoil fluids (0W-20 & ATF) in both of my Honda vehicles with no issues, so I am a firm believer in using synthetic lubricants. I have always heard that using synthetic instead of conventional engine oil will result in lower operating temperatures. I have often wondered about this, because I thought that the thermostat actually maintains the engine temperature when it opens/closes to control the amount of heat removal.

Perhaps the short answer is that there is less heat to remove when using synthetics, which results in the thermostat having to open less frequently? If this is incorrect, can someone really make the statement that using a synthetic engine oil results in lower operating temperatures when taking the thermostat into consideration?

The above question only applies to engine oil. I realize that automatic transmissions are a completely different application.

 

[Steve S]

coolant temps and oil temps are two different things.

 

[rg200amp]

Well, In theory Synthetic oil lubes better then conventional. So the better lube will cause less friction inside the motor. We all know friction causes heat. So the idea is less friction, less heat.

It will not be a major improvment, but people have seen 2-6 degrees less when useing good synthetics.

 

[bmwtechguy]

Theoretically, your engine will operate cooler with synthetic oil. I believe that synthetics can transfer heat a tad better and can lower friction somewhat, contributing to lower temps, but like you say, the thermostat does keep the engine up to a certain temp for good reason. Best thing I can say is take your infrared temp gun and take readings in different places with one type of oil or the other in the sump under same conditions if possible. Then you may see small differences of temp in some regions, like the oil pan sump. I think that bigger differences in temp will be seen in the rest of the powertrain components such as the transmission or differential.

 

[simple_gifts]

Quote:

So the idea is less friction, less heat.


An in theory the engine should convert more of the combustion energy into power....

 

[artificialist]

Since there is less friction generating heat, the engine coolant temperature will not rise as quickly, however, it will be enough to rise to operating temperature if you drive far enough.

 

[rg200amp]

Originally Posted By: simple_gifts
Quote:

So the idea is less friction, less heat.


An in theory the engine should convert more of the combustion energy into power....



Yes, in theory, less friction means theres less drag on the motor, thus it can produce more power.

There are dynos showing this, but the gains are in the single digits. Nothing that you can really feel.


Also, it will not lessen the warmup time of your motor. The act of fuel and air exploding in a metal cylinder will get the engine to operating temp with in the same amount of time, give or take 20-80 seconds approx.

 

[scoobie]

I thought that most of the heat comes from the gasoline exploding inside of the cylinders. The heat has to be carried away by the oil. Your synthetic oil may have better flow properties than a conventional, but I think you'll find that study of the hot viscosity would be of interest, and the main difference would be in the friction modifier additives. I personally run 50:50 conventional synthetic, with a shot of promoly, and my wife reports the engine loves it, silent at all speeds. The computer gas mileage confirms the engine is running optimally. I think the frictional heat is very minimal, compared to the heat coming from the gasoline exploding inside the combustion chamber.

 

[mechtech2]

Thin oil will run cooler than a thick oil. About 10 deg at full operating temp.
But synthetic cooler than dino? I don't see how or why it would operate cooler just because it is full synthetic.

And like the guys said, the water temp is pretty stable because of the thermostat. Engine oil is subject to ambient conditions, with no regulatory device.

 

[rg200amp]

FULL Synthetics usally reduces friction better then dino.

It is marginal yes, but there is still a slight difference.
*Note that not all synthetics are better then dinos. But for all the major brand names this rule usally applies.

If you use a group I value store dino, then use a Group V synthetic like Redline or Neo you will see less friction with the group V. Thus less heat(not noticable**like 1-2 degrees some times even less) and more power(again not noticable**pending on the motor+mods)

Its when you get into the Group III,IV, and sometimes V oils when the out come of which is better to reduce friction gets clouded. with those oils, pending on the brand. It depends more on there additive rather than there base oil.


The motor produces its heat from combustion. The little heat made from friction, for the most part, has nothing to do with the operating temp of that motor.

 

[Jim Allen]

I ran across some materials a few months back that says synthetics do not transfer heat quite as well as conventional. A small difference. It's in my pile stuff to file but I can't find it. It had to do with gear oil, as I recall. I'm not saying it's verified, but it was from reasonably solid sources. I not going to waste a lot of time looking (I'm servicing all my yard equipment today), but if I turn it up soon, I'll reference it.

With regard to gear oil, I have personally seen 15 degree reductions in gear oil temps in back-to-back identical tests of synthetic versus conventional. That said, I have also seen friction-reducing additives in gear oil achieve the same results. Stands to reason the effects of both methods would be similar in an engine, though the numbers would vary.

 

[mpersell]

Synthetics ability to deal with heat is one of the advantages as well. If you have high underhood temp built in and you live in somewhere hot you have extra protection from your driving environment.

These are all soft benefits in that we don't see immediate tangible results but over the years we've seen the compiled evidence in a lot of vehicles, equipment.

 

[rg200amp]

I do not think comparing gear oils abilty to disapate heat and motor oils abilty is the right test for this application.

 

[Liquid_Turbo]

Here's my take:

Previous comments about reduced friction due to synthetic viscosities vs conventional viscosities will be negligible.

The real question lies in the ability for oil to transfer heat. (ie. Conventional vs Synthetic's heat transfer coefficient). The flowing oil acts as a 'heat sink' to wick heat away from the surfaces it flows over.

Now, we all know syns are better handle thermal stress from heat. The real question is determining the heat transfer coefficients of the two liquids.

 

[Doug Hillary]

Hi,
Liquid_Turbo - Whilst relatively small, friction is an issue - due to their structure (various) synthetics do flow in a more linear manner and with less "friction"

 

[Liquid_Turbo]

My meaning is that the heat differences caused by differences in flow characteristics of the two types of oil will be negligible, compared to the fluid heat transfer properties of the two type of oils.

 

[EagleFTE]

Originally Posted By: Lyondellic
I have always heard that using synthetic instead of conventional engine oil will result in lower operating temperatures. I have often wondered about this, because I thought that the thermostat actually maintains the engine temperature when it opens/closes to control the amount of heat removal.


I don't know what the overall impact of a good syn is in a liquid cooled engine. I suspect your thoughts are correct. But if the question is does a good synthetic lower temps (ignoring thermostat controlled engine cooling system) I can tell you that there are many, many observations of lowered temps in air cooled engines using oils such at M1 Vtwin, Amsoil, Red Line and other high quality oils. Often people observe a 20 degree reduction or better in an air cooled V=twin engine on "canned" drives in similar/same conditions like to and from work on the same route every day. Reductions from 250 down to 220 or better are not uncommon at all.

 

[Doug Hillary]

Hi,
EagleFTE - Your experience with air cooled engines mirrors mine to a large degree

The temperature variance results are well known in differentials and gearboxes

 

[EagleFTE]

Originally Posted By: Doug Hillary
Hi,
EagleFTE - Your experience with air cooled engines mirrors mine to a large degree

The temperature variance results are well known in differentials and gearboxes


That makes sense based on what we see in the air cooled bikes. It is almost a shame on the bikes that you spend a little more to get the temp stability of a Group IV/V product and the first thing that happens is it lowers the operating temp back into the comfort zone. But thats ok. Like I've said before, I've never lost any sleep worrying that my oil is too good.