5w20 cooler engine than 5w30

[nicholas]

Hi everyone

Just curious if anyone knows this.....
Assuming same engine same ambient temps, same highway driving,load.

Does a 5w20 allow an engine, perhaps the heads run cooler than a 5w30.

I have been looking everywhere but can't really find anything.

Both my cars won't give this info through live data obd2. Otherwise I would try it myself.

Thanks

 

[dumkid]

From the other 243 threads on this subject (thicker=hotter?) I don't know if I've ever seen a clear answer. If there is a difference, it's not a big difference

 

[Jetronic]

Minimal difference in head temperatures I suspect. Even less if it's an OHV head vs OHC.

 

[Al]

I have run 0W-20 and 0-40 in the same engine and the oil temperature difference is not noticeable. Oil temperature mirrors water temp which is controlled by a thermostat

 

[twX]

In theory, there will be lower friction losses with the thinner oil, most of which is in the piston area. This is why fuel economy is better with thinner oils. The oil will experience less direct heating from friction, and the engine won't be burning quite as much fuel, so there should be a bit less heat transferred through the head and cylinder walls.

You won't notice a change in coolant temperatures, since they're so well-regulated. Oil temperature may be lower, but probably not by a whole lot. I'll be switching from 5W-30 to 0W-20 for winter soon, and I've got a lot of previous datalogs with the 5W-30, so I'll probably do a comparison in the same conditions. The car has a oil-coolant heat exchanger, so I doubt the difference will be noticeable.

 

[Propflux01]

Any thinner liquid will transfer heat better than a thicker one. But that can also be assumed that there is an equal flow of liquid over the heated object.

 

[oldhp]

With winter coming then I want hotter oil. 20W50 it is.

 

[KrisZ]

In theory, there will be lower friction losses with the thinner oil, most of which is in the piston area. This is why fuel economy is better with thinner oils. The oil will experience less direct heating from friction, and the engine won't be burning quite as much fuel, so there should be a bit less heat transferred through the head and cylinder walls.

You won't notice a change in coolant temperatures, since they're so well-regulated. Oil temperature may be lower, but probably not by a whole lot. I'll be switching from 5W-30 to 0W-20 for winter soon, and I've got a lot of previous datalogs with the 5W-30, so I'll probably do a comparison in the same conditions. The car has a oil-coolant heat exchanger, so I doubt the difference will be noticeable.

That is incorrect and thinking this way leads to myths like there thicker oils cause more wear.

There is no change in internal engine component frictional losses, but there is a change in pumping losses. A less viscous liquid requires less energy to pump though the same system. That's where the fuel economy gains come from.

 

[twX]

There is no change in internal engine component frictional losses, but there is a change in pumping losses. A less viscous liquid requires less energy to pump though the same system. That's where the fuel economy gains come from.

All of the studies I've seen that look at an oil's effect on fuel efficiency are focused on friction between the pistons and cylinder walls. Oil pumps will use less power as well, but those losses aren't as significant.

That is incorrect and thinking this way leads to myths like there thicker oils cause more wear.

Lower friction doesn't necessarily equate to lower wear. I've seen a study showing thinner oil reducing friction while increasing wear. Also, if an oil is too thin, it can actually increase friction as well.

 

[KrisZ]

All of the studies I've seen that look at an oil's effect on fuel efficiency are focused on friction between the pistons and cylinder walls. Oil pumps will use less power as well, but those losses aren't as significant.

View attachment 184378


Lower friction doesn't necessarily equate to lower wear. I've seen a study showing thinner oil reducing friction while increasing wear. Also, if an oil is too thin, it can actually increase friction as well.

Well, that charts shows how the friction drastically increases with RPM, I do not see how oil viscosity plays a role here.

 

[gfh77665]

I have run 0W-20 and 0-40 in the same engine and the oil temperature difference is not noticeable. Oil temperature mirrors water temp which is controlled by a thermostat

THIS ^^^ In real life you will never notice anything.

 

[meep]

4 wheel magazine instrumented a drivetrain years ago in an in-depth article on driveline cooling. Their data showed where thinner oil kept gears cooler, carrying the heat outward to the case. This is a big deal in towing applications, and a strong argument for staying with 90 wt oils when called for it in driveline components.

I posted data from an allpar article a few times over the last 2 decades where a Chrysler engineer discussed their factory findings for thick vs thin results and one of the points was this: valvetrain wear was less with thin oils, while bottom end wear was less with thicker oils, and the chain didn’t go hydrodynamic with 5-30 until somewhere around 1500 rpm.