Engine oil cleaning ability vs Oil temperature

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I have been reading about different engine oils cleaning abilities here on the forum
but have not seen much regarding how engine oils cleaning ability is affected
by the oil temperature.
Does the detergents in the oil need to reach a certain temperature to be effective?
 
For cleaning they have to be at high temperature. That's the whole idea of the italian tuneup.

Heat speeds up the rate of a chemical reaction and there is mechanical force which probably helps as well.
 
Here's the solubility of varnish in turbine oil (very low additive levels) with temperature...
 
Yep, the additives are temperature activated....which then makes me wonder what those temperatures are, and do the additives 'deactivate' at the same point?

For example, my motorcycle has a 160F thermostat. In warmer ambient temperatures, I can easily get the oil to hit, say, 200F, but on cooler days a sustained run at freeway speeds can bring oil temps down into the 150-160 range (bike has a coolant-to-oil heat exchanger). Did some of those additives 'deactivate' as the oil temperatures dropped?
 
Originally Posted By: jeff78
Yep, the additives are temperature activated....which then makes me wonder what those temperatures are, and do the additives 'deactivate' at the same point?

For example, my motorcycle has a 160F thermostat. In warmer ambient temperatures, I can easily get the oil to hit, say, 200F, but on cooler days a sustained run at freeway speeds can bring oil temps down into the 150-160 range (bike has a coolant-to-oil heat exchanger). Did some of those additives 'deactivate' as the oil temperatures dropped?


I've wondered the same thing about the triblolayer of zinc. What temp does it require to form?

Question for molakule.
 
I have seen results of a test of the thickness of the zinc layer; results were that it gets thicker up to 150C. I'll post the graph (of the thickness of the layer relative to temperature) when I can find it.

This is interesting to know about the cleaning abilities. I had no idea those additives were heat activated as well.

EDIT: Of course I can't find it--but the thickness was 30 nanometers at 150C, whereas at lower temps it was just 2-3 nm.

EDIT: Looks like I was mistaken on the 30 nm figure. This is the chart I was thinking of:




The document explaining this was found here: https://www.researchgate.net/publication...3D&el=1_x_2

Originally Posted By: spasm3


I've wondered the same thing about the triblolayer of zinc. What temp does it require to form?

Question for molakule.
 
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You would think the additives are designed for nominal engine temps and you wouldnt need an Italian tuneup to "activate" it!
 
I use a quality oil and never "Italian Tune-Up" my engine even though I am Italian. My engines have always been spotlessly clean even with long OCI's. ?!?
 
Originally Posted By: StevieC
I use a quality oil and never "Italian Tune-Up" my engine even though I am Italian. My engines have always been spotlessly clean even with long OCI's. ?!?


Maybe by nature you drive like Italians and don't know it
shocked2.gif
I see a lot of Italian wannabes on packed freeways everyday
grin2.gif
 
I think 80C+ is good for the anti-wear additives, the sequence IV wear test is done at 60 or 65C? It’s the transition zone where the oil has thinned enough that the boundary lubrication additives are needed but they aren’t fully activated yet.

Cleaning additives I assume hotter is better as long as your not coking oil in hotspots.
 
Originally Posted By: camrydriver111
For cleaning they have to be at high temperature. That's the whole idea of the italian tuneup.


The "Italian" tune up is more about blowing the carbon out.
 
Originally Posted By: SilverFusion2010
... Cleaning additives I assume hotter is better as long as your not coking oil in hotspots.
To get back to the original question, that summary seems highly plausible, unless someone comes along with evidence to the contrary.
 
I fully expect it is the same as what’s taught in chemistry classes: higher temperatures increases the rate of a solvent dissolving a solute as well as how much solute the solvent can keep in solution, given enough time to dissolve.
 
For the same reason doing dishes or laundry with warm water works better than cold water, hotter oil cleans (dissolves deposits) better.

It's a combination of additive activation at higher temperatures and increasing solvency of the base oil at higher temperatures.

In addition, thinner base oils have lower aniline points, which means higher solvency. (Aniline point = lowest temperature at which an oil can fully dissolve aniline.) Therefore, at a given temperature, a 0W-xx base oil will clean better than a 5W-xx base oil of the same type.

See the section under solubility. A lower aniline point or a higher kauri-butanol value indicate higher solvency:

https://www.tri-iso.com/documents/exxonmobil_chemical_spectrasyn_plus_Brochure.pdf
 
Originally Posted By: Shannow
Here's the solubility of varnish in turbine oil (very low additive levels) with temperature...



So if i have some minor varnish in my B230 Volvo redblock then the Redline 5w30
that i use now will benefit from a slightly higher operating temperature to remove it?
 
Originally Posted By: magnus308
Originally Posted By: Shannow
Here's the solubility of varnish in turbine oil (very low additive levels) with temperature...



So if i have some minor varnish in my B230 Volvo redblock then the Redline 5w30
that i use now will benefit from a slightly higher operating temperature to remove it?


Not that simple...you don't "lay down" varnish until the oil is "full" to saturation...then it finds a cold spot an dops out. It's highly polar, and sticks to metal, then stick to itself.

fresh, hot oil WILL pick it up, but can't hold much.

I've done 600 mile oil changes with mineral oil to try to shift varnish but by the time you've noticed it, that won't work.

For turbines, there are electrostatic machines that will remove varnish from the oil, allowing the oil to pick up deposits and ultimately remove it...but that's thousands of operational hours with the machine running and the electrostatics in service.
 
Not sure what you mean when you say "full to saturation".... Could you explain?

Originally Posted By: Shannow

Not that simple...you don't "lay down" varnish until the oil is "full" to saturation...then it finds a cold spot an dops out.
 
Originally Posted By: paulri
Not sure what you mean when you say "full to saturation".... Could you explain?


Look at the video I linked, and play it backwards in your head...

As the oil cools, it's ability to hold the varnish reduces. If the oil is only holding a little bit, it might be able to stay dissolved as the temperature drops.

If the oil is holding nearly as much as it can while hot, it has to release it.

As an aside where the varnish is formed isn't necessarily where you find the deposits. e.g. on turbines, it's formed in the bearings and hydrogen seals (return oil pipes too if earthing is poor), but usually FOUND in the governor.
 
So oil will hold varnish until it has no more capacity, and then it will lay it down on the engine.
 
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