They then went onto say that modern cars do lose oil and at 14k miles it was due a service which is why it need oil
Is this true or a load of boloney
Old or modern, all engines use oil, even when new. Depends on the engine. If some are churned out with deteriorating unchecked tolerances or badly designed piston rings, e.g. some 'Prince' engines, it will use more oil than a well made engine. Size and number of cylinders are also a factor. My ancient 4 cylinder TR7 engine uses less oil than my much newer Audi 12 cylinder - same mileage c.72000. Type of oil is also a factor; in contrast to the classic gloopy 20-50 grade, modern 0-30 oils seem to be hardly more viscous than Ribena.
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They then went onto say that modern cars do lose oil and at 14k miles it was due a service which is why it need oil
Is this true or a load of boloney
Baloney?
Not really. By 14k miles the oil is very probably worn out. By worn out, I mean that the ability of the oil to retain it's hot viscosity is wearing out, the molecular bonds that hold the oil together to retain it's hot viscosity are letting go, so the oil is thinner at higher temperatures so consequently the engine will use more oil as it passes the piston rings easier - noticeable with mineral oils.
If you've ever run cars hard, say a company car, and gone over the oil change interval, you may have noticed that around that time the engine will start to use more oil than it did. That's why, particularly if you are running a mineral oil.
Hence manufacturers specify synthetic oils - they hold together better for longer.
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They then went onto say that modern cars do lose oil and at 14k miles it was due a service which is why it need oil
Is this true or a load of boloney
Baloney?
Not really. By 14k miles the oil is very probably worn out. By worn out, I mean that the ability of the oil to retain it's hot viscosity is wearing out, the molecular bonds that hold the oil together to retain it's hot viscosity are letting go, so the oil is thinner at higher temperatures so consequently the engine will use more oil as it passes the piston rings easier - noticeable with mineral oils.
If you've ever run cars hard, say a company car, and gone over the oil change interval, you may have noticed that around that time the engine will start to use more oil than it did. That's why, particularly if you are running a mineral oil.
Hence manufacturers specify synthetic oils - they hold together better for longer.
I don't know for an absolute fact that this is wrong, and don't have time to look for evidence (which will be hard, maybe impossible, to find) but it seems unlikely.
My understanding is that most viscosity loss in multigrade oils is due to viscosity improver (VI) shear, not degradation or shear of the base oil.
Thus mineral straight grade oils have very good viscosity retention since they contain no VI's, and so offer superior lubrication in hot climates.
The oil here will probably be a synthetic with a low base viscosity, 0 or 5, but its high temperature viscosity will be mostly contributed by viscosity improvers.
Its high temperature viscosity stability will thus not be much influenced by greater stability of the base oil, and will only be superior if it has more stable viscosity improvers.
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They then went onto say that modern cars do lose oil and at 14k miles it was due a service which is why it need oil
Is this true or a load of boloney
Baloney?
Not really. By 14k miles the oil is very probably worn out. By worn out, I mean that the ability of the oil to retain it's hot viscosity is wearing out, the molecular bonds that hold the oil together to retain it's hot viscosity are letting go, so the oil is thinner at higher temperatures so consequently the engine will use more oil as it passes the piston rings easier - noticeable with mineral oils.
If you've ever run cars hard, say a company car, and gone over the oil change interval, you may have noticed that around that time the engine will start to use more oil than it did. That's why, particularly if you are running a mineral oil.
Hence manufacturers specify synthetic oils - they hold together better for longer.
I don't know for an absolute fact that this is wrong, and don't have time to look for evidence (which will be hard, maybe impossible, to find) but it seems unlikely.
My understanding is that most viscosity loss in multigrade oils is due to viscosity improver (VI) shear, not degradation or shear of the base oil.
Thus mineral straight grade oils have very good viscosity retention since they contain no VI's, and so offer superior lubrication in hot climates.
The oil here will probably be a synthetic with a low base viscosity, 0 or 5, but its high temperature viscosity will be mostly contributed by viscosity improvers.
Its high temperature viscosity stability will thus not be much influenced by greater stability of the base oil, and will only be superior if it has more stable viscosity improvers.
https://www.api.org/~/media/Files/Certification/Engine-Oil-Diesel/Publications/4-Trends-in-Shear-Stability-of-Automotive-Engine-Oils.pdf
Tends to confirm that behaviour is dominated by the VI's. and that it is not as predictable as you suggest.For example
"The low shear results on several 5W-30 oils revealed some interesting behavior. The sheared or degraded oil had higher viscosity results than the fresh oil at 100 °C.
Both the dynamic viscosity and the kinematic viscosity results showed the same trend. • This behavior of viscosity increase with shear was observed primarily on 5W-30 oils, and primarily those purchased in Europe. •
This trend has been growing over the last several years and is spreading to the other regions of the world.
Based on the performance of the oils, the stay-in-grade requirements appear to an important criteria for the formulators (particularly the 5W-30 oils in Europe)."
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<< ... in contrast to the classic gloopy 20-50 grade, modern 0-30 oils seem to be hardly more viscous than Ribena. >>
Neat, or as you drink it ?
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Neat. (It doesn't seem to be as gloopy as it used to be).
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"My understanding is that most viscosity loss in multigrade oils is due to viscosity improver (VI) shear, not degradation or shear of the base oil.
Thus mineral straight grade oils have very good viscosity retention since they contain no VI's, and so offer superior lubrication in hot climates."
That's not my professional experience.
The climate doesn't really come into it - an engine runs at it's cooling system's set temperature.
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"My understanding is that most viscosity loss in multigrade oils is due to viscosity improver (VI) shear, not degradation or shear of the base oil.
Thus mineral straight grade oils have very good viscosity retention since they contain no VI's, and so offer superior lubrication in hot climates."
That's not my professional experience.
The climate doesn't really come into it - an engine runs at it's cooling system's set temperature.
An engine starts at ambient temperature which is why we have multi grade oils
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"My understanding is that most viscosity loss in multigrade oils is due to viscosity improver (VI) shear, not degradation or shear of the base oil.
Thus mineral straight grade oils have very good viscosity retention since they contain no VI's, and so offer superior lubrication in hot climates."
That's not my professional experience.
The climate doesn't really come into it - an engine runs at it's cooling system's set temperature.
An engine starts at ambient temperature which is why we have multi grade oils
So the cold rating, eg 5W should vary with climate but not the hot rating, eg -30
For several decades, I've used the lowest cold rating available which meets the manufacturers ACEA specification and whatever hot rating is specified - my logic is that most wear occurs when the engine is cold so the faster it gets protected the better.
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"My understanding is that most viscosity loss in multigrade oils is due to viscosity improver (VI) shear, not degradation or shear of the base oil.
Thus mineral straight grade oils have very good viscosity retention since they contain no VI's, and so offer superior lubrication in hot climates."
That's not my professional experience.
The climate doesn't really come into it - an engine runs at it's cooling system's set temperature.
An engine starts at ambient temperature which is why we have multi grade oils
So the cold rating, eg 5W should vary with climate but not the hot rating, eg -30
For several decades, I've used the lowest cold rating available which meets the manufacturers ACEA specification and whatever hot rating is specified - my logic is that most wear occurs when the engine is cold so the faster it gets protected the better.
Counter arguments include:,
For a positive displacement pump like the oil pump, within the limits of the oils pumpability, there is little or no difference in the time it takes for oil to be pumped to the top end.
Thicker oil doesn't drain down from the top end so fast as thin oil, so is already there.
The only data (as opposed to advertising claims and opinions probably founded on same) that I've seen suggests the difference in oiling time was very small (seconds) though there was a slight difference.
It was, however, a rather limited and possibly flawed study. IIRC cam oiling time was estimated from the noise.
For a straight grade oil there is of course no "cold" grade. I could probably get away with straight SAE40 here in Taiwan,(SAE30 is recommended) but so far I've cut it 50:50 with 15W40 or 20W50, which probably gives me about 20W40 - 25W40. Seems OK, and cleared some varnish deposits.
Edited by edlithgow on 18/03/2022 at 02:03
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