I saw a pour test from Pennzoil awhile back depicting the difference in pour quality between used and new oil, and the used oil wasn't pouring as fast into the beaker. Made me curious about how much oil thickens over time or if it even does it at all? This could be an advertising ploy to get people to change oil more often, oil companies don't make money if people aren't changing oil so they could've froze the used oil and warmed up the new stuff to make it look drastically different. What would cause used oil to potentially thicken up? And would this be a problem in a extreme cold climate like Montana if the oil was getting aged but not quite ready to be changed yet? I ask because my rigs sit outside all winter with no block heaters of any kind and I try to time it where the oil is changed in the spring and fall so I don't have to be laying in the snow in the cold doing it cussing up a blue streak.
Does oil thicken with use?
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I think oil typically gets thinner with use due to shearing, and fuel dulution to some degree. But it can also thicken slighty due to volitility evaporation - multiple things going on.
Attached is a good collection of UOAs on V8 Mustang engines. As you can see most of the oils thinned down, but a few got slightly thicker. Compare the Used vs Virgin viscosity data. The colored groups in the left column are different oils that were used in the same car.
Attached is a good collection of UOAs on V8 Mustang engines. As you can see most of the oils thinned down, but a few got slightly thicker. Compare the Used vs Virgin viscosity data. The colored groups in the left column are different oils that were used in the same car.
It is not so much that the oil thickens up, it is that low temperature performance can worsen in aged oil.
If you change your oil just before winter in a very cold climate, you'll probably be ok. If you want to use oil over two winters, you might be better off going with a majority PAO oil such as Mobil 1 0w20 EP.
If you change your oil just before winter in a very cold climate, you'll probably be ok. If you want to use oil over two winters, you might be better off going with a majority PAO oil such as Mobil 1 0w20 EP.
Some oils decidedly thicken and don't shear, Mobil 1 V-Twin starts out a 20W-50 but a lot of times ends up thickening to almost 60.
I'm hoping when my 60 thins down to a 30, it'll thicken up to a 40.
Typical multigrades thin as service commences and then thicken as oxidation takes place.
Back in the day, M1 0W40 was a master at it.
However "stay in grade" for the W rating allows it to slip a grade in service, so a 0W can become a 5W and still be compliant.
As others have said, the cold performance is the most likely to suffer...and it's the least likely to be tested in a used oil.
Back in the day, M1 0W40 was a master at it.
However "stay in grade" for the W rating allows it to slip a grade in service, so a 0W can become a 5W and still be compliant.
As others have said, the cold performance is the most likely to suffer...and it's the least likely to be tested in a used oil.
Probably depend on the oil, particularly on the quantity and quality of anti-oxidant and viscosity index improver.
Wide range multigrades will likely shear initially, then oxidatively thicken toward end-of-life.
Straight grades won't shear much so will just show a rise in oxidative thickening.
IIRC, due to the more complex makeup wrt oxidative sites, Group I base oils tend to thicken gradually over the service life, while with higher Groups the rise is delayed, but more sudden when it occurs.
Wide range multigrades will likely shear initially, then oxidatively thicken toward end-of-life.
Straight grades won't shear much so will just show a rise in oxidative thickening.
IIRC, due to the more complex makeup wrt oxidative sites, Group I base oils tend to thicken gradually over the service life, while with higher Groups the rise is delayed, but more sudden when it occurs.
I would think soot from blow by would cause oil to turn black and thicken.
Sometimes, sometimes it stays in grade, and other times it gets thinner. It depends.........
Originally Posted by CharlieBauer
It is not so much that the oil thickens up, it is that low temperature performance can worsen in aged oil.
If you change your oil just before winter in a very cold climate, you'll probably be ok. If you want to use oil over two winters, you might be better off going with a majority PAO oil such as Mobil 1 0w20 EP.
Is AFE 0W-30 majority PAO? That's what I use in my Tacoma.
It is not so much that the oil thickens up, it is that low temperature performance can worsen in aged oil.
If you change your oil just before winter in a very cold climate, you'll probably be ok. If you want to use oil over two winters, you might be better off going with a majority PAO oil such as Mobil 1 0w20 EP.
Is AFE 0W-30 majority PAO? That's what I use in my Tacoma.
Don't forget fuel dilution. The original multigrade
There are two phases in mechanical oil quality change:
1) it gets diluted and thus gets thinner
2) lighter fractions evaporate including gas in oil that actually accelerates evap and oil gets thicker
So, expect oil with 4k miles on it be thinner that new, while oil with 15K miles on it being thicker.
1) it gets diluted and thus gets thinner
2) lighter fractions evaporate including gas in oil that actually accelerates evap and oil gets thicker
So, expect oil with 4k miles on it be thinner that new, while oil with 15K miles on it being thicker.
Forgot #3 ... it mechanically shears between two moving surfaces and becomes thinner. It would have to evaporate a lot of volitiles to make up for that, depending on the engine. Some engines will shear oil much more than others.
It does oxidize. Usually this is after it shears.
Originally Posted by ZeeOSix
Some engines will shear oil much more than others.
Originally Posted by dave1251
It does oxidize. Usually this is after it shears.
The oil never shears as far as I know, the hydrocarbon chains are very small. But it can oxidize.
If you mean that the VII shear then that is possible but it is dependent on the quality of the VII and the specific design of the engine.
Some engines will shear oil much more than others.
Originally Posted by dave1251
It does oxidize. Usually this is after it shears.
The oil never shears as far as I know, the hydrocarbon chains are very small. But it can oxidize.
If you mean that the VII shear then that is possible but it is dependent on the quality of the VII and the specific design of the engine.
Originally Posted by ZeeOSix
Attached is a good collection of UOAs on V8 Mustang engines. ....
Whats the deal with that Moly level on line 30??
Attached is a good collection of UOAs on V8 Mustang engines. ....
Whats the deal with that Moly level on line 30??
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