Faster warm-up times, better (marginally) gas mileage.
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0W-20 or 5W-20?
- Thread starter Dave Sherman
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0w-20 on sale at a chain parts store. I'm using Mobil 1 0w-20 in the Fit with 10k+ OCI's, per Honda recommendations. It starts a little better in the cold than with 5w20 conventional. I got 10 quarts of Mobil 1 0w-20 and 2 Mobil 1 filters for a tick over $60.
Originally Posted By: fokvoort
Originally Posted By: d00df00d
xw-20 just means 5w-20 or 0w-20.
I know; I'm curious what the benefit of an xW-20 is over an xW-30.
Ah, okay. My apologies.
AFAIK: In general, the benefits of a thinner oil are:
- Faster/easier flow
- Better cooling
- Less tendency to trap air bubbles
- Less parasitic drag (this is how it improves fuel economy)
These of course have to be balanced against lower oil pressure and thinner films, which is why not all cars use xw-20s.
Originally Posted By: d00df00d
xw-20 just means 5w-20 or 0w-20.
I know; I'm curious what the benefit of an xW-20 is over an xW-30.
Ah, okay. My apologies.
AFAIK: In general, the benefits of a thinner oil are:
- Faster/easier flow
- Better cooling
- Less tendency to trap air bubbles
- Less parasitic drag (this is how it improves fuel economy)
These of course have to be balanced against lower oil pressure and thinner films, which is why not all cars use xw-20s.
Originally Posted By: fokvoort
Originally Posted By: ericthepig
Fokvoort - it's been long established that the xw20s do fine in the heat. There are a bizillion police crown vics running 5w20s in hot summers/high speeds.
Good to know. Does the xW-20 run a little thinner at operating temps? I seem to recall this is a weight that is chosen for better economy...
Should we call you Fok or Voort?
Concerning fuel economy - my BITOG readings of numerous post on this subject is that fuel econ. will be undetectable between a 0w20 and 5w20. All oils end up at about the same viscosity at OP temp - even for a 0w20 vs a 15w40. However, the increase (at 15w40) of HTHS apparently does play a role in this (high HTHS=lower fuel econ) - however most real world posts I've seen indicate if your doing medium or long commutes, the diff is hard to detect. Short commutes meanwhile play in the 0w20's favor since a (eg) 15w40 is "much" thicker in a cool engine. Also, the OEMs apparently believe the 0w20s are helping fuel econ. - so that too had to be considered.
Originally Posted By: ericthepig
Fokvoort - it's been long established that the xw20s do fine in the heat. There are a bizillion police crown vics running 5w20s in hot summers/high speeds.
Good to know. Does the xW-20 run a little thinner at operating temps? I seem to recall this is a weight that is chosen for better economy...
Should we call you Fok or Voort?
Concerning fuel economy - my BITOG readings of numerous post on this subject is that fuel econ. will be undetectable between a 0w20 and 5w20. All oils end up at about the same viscosity at OP temp - even for a 0w20 vs a 15w40. However, the increase (at 15w40) of HTHS apparently does play a role in this (high HTHS=lower fuel econ) - however most real world posts I've seen indicate if your doing medium or long commutes, the diff is hard to detect. Short commutes meanwhile play in the 0w20's favor since a (eg) 15w40 is "much" thicker in a cool engine. Also, the OEMs apparently believe the 0w20s are helping fuel econ. - so that too had to be considered.
Originally Posted By: d00df00d
Ah, okay. My apologies.
AFAIK: In general, the benefits of a thinner oil are:
- Faster/easier flow
- Better cooling
- Less tendency to trap air bubbles
- Less parasitic drag (this is how it improves fuel economy)
These of course have to be balanced against lower oil pressure and thinner films, which is why not all cars use xw-20s.
Excellent explanation -- thank you.
Most make sense to me, but I'm fuzzy on why it would have less a tendency to trap air bubbles, and why oil pressure would be lower...
Ah, okay. My apologies.
AFAIK: In general, the benefits of a thinner oil are:
- Faster/easier flow
- Better cooling
- Less tendency to trap air bubbles
- Less parasitic drag (this is how it improves fuel economy)
These of course have to be balanced against lower oil pressure and thinner films, which is why not all cars use xw-20s.
Excellent explanation -- thank you.
Most make sense to me, but I'm fuzzy on why it would have less a tendency to trap air bubbles, and why oil pressure would be lower...
Originally Posted By: ericthepig
Should we call you Fok or Voort?
Either or both is fine.
Originally Posted By: ericthepig
Concerning fuel economy - my BITOG readings of numerous post on this subject is that fuel econ. will be undetectable between a 0w20 and 5w20. All oils end up at about the same viscosity at OP temp - even for a 0w20 vs a 15w40. However, the increase (at 15w40) of HTHS apparently does play a role in this (high HTHS=lower fuel econ) - however most real world posts I've seen indicate if your doing medium or long commutes, the diff is hard to detect. Short commutes meanwhile play in the 0w20's favor since a (eg) 15w40 is "much" thicker in a cool engine. Also, the OEMs apparently believe the 0w20s are helping fuel econ. - so that too had to be considered.
Makes sense and good to know. Thank you.
Should we call you Fok or Voort?
Either or both is fine.
Originally Posted By: ericthepig
Concerning fuel economy - my BITOG readings of numerous post on this subject is that fuel econ. will be undetectable between a 0w20 and 5w20. All oils end up at about the same viscosity at OP temp - even for a 0w20 vs a 15w40. However, the increase (at 15w40) of HTHS apparently does play a role in this (high HTHS=lower fuel econ) - however most real world posts I've seen indicate if your doing medium or long commutes, the diff is hard to detect. Short commutes meanwhile play in the 0w20's favor since a (eg) 15w40 is "much" thicker in a cool engine. Also, the OEMs apparently believe the 0w20s are helping fuel econ. - so that too had to be considered.
Makes sense and good to know. Thank you.
Originally Posted By: fokvoort
Most make sense to me, but I'm fuzzy on why it would have less a tendency to trap air bubbles,
That was a clumsy way of saying its foaming tendency is lower. Thinner oil releases air bubbles more readily, so fewer remain trapped.
Originally Posted By: fokvoort
and why oil pressure would be lower...
I would try to explain, but I'm sure I would make a hash of it. I will have to defer this explanation to someone better informed and more articulate.
Most make sense to me, but I'm fuzzy on why it would have less a tendency to trap air bubbles,
That was a clumsy way of saying its foaming tendency is lower. Thinner oil releases air bubbles more readily, so fewer remain trapped.
Originally Posted By: fokvoort
and why oil pressure would be lower...
I would try to explain, but I'm sure I would make a hash of it. I will have to defer this explanation to someone better informed and more articulate.
Originally Posted By: ericthepig
(high HTHS=lower fuel econ)
Not necessarily.
Originally Posted By: Tom NJ
Lots of variables here make this a complex topic. In a Newtonian fluid (no VI Improvers or similar large polymers), there would be a direct correlation between kinematic viscosity and HTHS viscosity. With VI Improvers, this correlation is often broken because the large molecules in the VI Improvers "flex" or compress under pressure (shear), sort of like a sponge. Therefore VI Improvers will increase the kinematic viscosity, but lose some of this thickening effect under high shear rates of the HTHS test. The amount of this molecular flexing or "temporary shear loss" depends on the quantity and type of VI Improver used, which varies from oil to oil. This is why you can find an oil with both a higher kinematic viscosity and a lower HTHS viscosity than another.
To help understand this, think of base oils as being steel balls and VI Improvers as being a rubber coating on these steel balls. Now, to make a straight 30 weight oil you would use a large (10 cSt) steel ball with no rubber coating. To make a 5w30 oil, you would start with a smaller (6 cSt) steel ball and add a rubber layer until the final ball is the same size as the straight 30 wt ball. Both balls are now the same size (same Kinematic viscosity), but when you squeeze this balls under pressure (HTHS viscosity) they will behave differently - the rubber coated steel ball will give (lose viscosity) while the uncoated steel ball will not. How much the rubber coated ball compresses depends on the thickness of the rubber layer (quantity of VI Improver) and the hardness of the rubber layer (type of VI Improver).
Kinematic viscosity is measured with no pressure (shear) and will give the same reading for both a straight 30 wt oil and a 5w30 oil. HTHS viscosity is measured under high shear rates and will give a lower number for the 5w30 oil (rubber coated ball) because it compresses the large VI Improver molecules. As the 5w30 oil compresses in the high shear areas of the engine it becomes a thinner oil and poses less internal frictional resistance.
As for the effect of these viscosities on fuel economy, most frictional losses occur in the bearings and ring/cylinder wall interface. Both of these areas are under high shear rates, so all else being equal the HTHS viscosity should correlate better with mileage than kinematic viscosity. Of course, all things are rarely equal, so friction modifiers, polar base oils, VI Improver quantity and type, engine shear rates, and temperature will have some influence on this correlation. Furthermore, if the HTHS viscosity gets too low, friction can increase as parts move into elastohydrodynamic or boundary regimes (Stribeck curve), so the correlation of HTHS viscosity to fuel economy is only valid within a range.
So in conclusion, fuel economy generally correlates to HTHS viscosity, except when it doesn't. grin
Tom NJ
Originally Posted By: High-Temperature, High-Shear Oil Viscosity: Measurement and Relation to Engine Operation by James A. Spearot
With regard to engine friction measurements, correlations with HTHS viscosity are documented for comparisons made in the same engine under the same operating conditions. However, even under well-controlled conditions, the friction-modifying properties of the DI package in each oil can influence the degree of correlation. Under cyclic engine-operating conditions, fuel economy measurements correlate better with HTHS viscosity than with kinematic viscosity.
The data referenced in DS-62 demonstrate several clear advantages of HTHS viscosity over kinematic viscosity in predicting engine performance. However, no single measure of oil rheology correlated perfectly with all of the engine parameters reviewed, probably because of the fact that each measure of engine performance is to some extent affected by both oil rheology and oil chemistry. Because of the variety of engines, oils and operating conditions used in the referenced works, the effects of oil rheology and oil chemistry are inextricably mixed.
There is more correlation with HTHS viscosity and fuel economy, but there is not necessarily a direct correlation.
(high HTHS=lower fuel econ)
Not necessarily.
Originally Posted By: Tom NJ
Lots of variables here make this a complex topic. In a Newtonian fluid (no VI Improvers or similar large polymers), there would be a direct correlation between kinematic viscosity and HTHS viscosity. With VI Improvers, this correlation is often broken because the large molecules in the VI Improvers "flex" or compress under pressure (shear), sort of like a sponge. Therefore VI Improvers will increase the kinematic viscosity, but lose some of this thickening effect under high shear rates of the HTHS test. The amount of this molecular flexing or "temporary shear loss" depends on the quantity and type of VI Improver used, which varies from oil to oil. This is why you can find an oil with both a higher kinematic viscosity and a lower HTHS viscosity than another.
To help understand this, think of base oils as being steel balls and VI Improvers as being a rubber coating on these steel balls. Now, to make a straight 30 weight oil you would use a large (10 cSt) steel ball with no rubber coating. To make a 5w30 oil, you would start with a smaller (6 cSt) steel ball and add a rubber layer until the final ball is the same size as the straight 30 wt ball. Both balls are now the same size (same Kinematic viscosity), but when you squeeze this balls under pressure (HTHS viscosity) they will behave differently - the rubber coated steel ball will give (lose viscosity) while the uncoated steel ball will not. How much the rubber coated ball compresses depends on the thickness of the rubber layer (quantity of VI Improver) and the hardness of the rubber layer (type of VI Improver).
Kinematic viscosity is measured with no pressure (shear) and will give the same reading for both a straight 30 wt oil and a 5w30 oil. HTHS viscosity is measured under high shear rates and will give a lower number for the 5w30 oil (rubber coated ball) because it compresses the large VI Improver molecules. As the 5w30 oil compresses in the high shear areas of the engine it becomes a thinner oil and poses less internal frictional resistance.
As for the effect of these viscosities on fuel economy, most frictional losses occur in the bearings and ring/cylinder wall interface. Both of these areas are under high shear rates, so all else being equal the HTHS viscosity should correlate better with mileage than kinematic viscosity. Of course, all things are rarely equal, so friction modifiers, polar base oils, VI Improver quantity and type, engine shear rates, and temperature will have some influence on this correlation. Furthermore, if the HTHS viscosity gets too low, friction can increase as parts move into elastohydrodynamic or boundary regimes (Stribeck curve), so the correlation of HTHS viscosity to fuel economy is only valid within a range.
So in conclusion, fuel economy generally correlates to HTHS viscosity, except when it doesn't. grin
Tom NJ
Originally Posted By: High-Temperature, High-Shear Oil Viscosity: Measurement and Relation to Engine Operation by James A. Spearot
With regard to engine friction measurements, correlations with HTHS viscosity are documented for comparisons made in the same engine under the same operating conditions. However, even under well-controlled conditions, the friction-modifying properties of the DI package in each oil can influence the degree of correlation. Under cyclic engine-operating conditions, fuel economy measurements correlate better with HTHS viscosity than with kinematic viscosity.
The data referenced in DS-62 demonstrate several clear advantages of HTHS viscosity over kinematic viscosity in predicting engine performance. However, no single measure of oil rheology correlated perfectly with all of the engine parameters reviewed, probably because of the fact that each measure of engine performance is to some extent affected by both oil rheology and oil chemistry. Because of the variety of engines, oils and operating conditions used in the referenced works, the effects of oil rheology and oil chemistry are inextricably mixed.
There is more correlation with HTHS viscosity and fuel economy, but there is not necessarily a direct correlation.
Dave Sherman
Thread starter
Thanks all for the info.
Originally Posted By: ChrisD46
Only real concern I see is price - I have yet to see PP or Mobil 1 0w20 at Walmart in a 5 quart jug . If you were to buy 0w20 in individual quarts - your oil change would just go up over $11.00 . A close alternative is Mobil 1 0w30 who many say is a thin 30 weight any way .
Good to know, I noticed Autozone only had 5 quart bottles of Mobil 1 0w-30. Going with 0w-20 or 5w-20 means having to buy quart bottles.
Originally Posted By: ChrisD46
Only real concern I see is price - I have yet to see PP or Mobil 1 0w20 at Walmart in a 5 quart jug . If you were to buy 0w20 in individual quarts - your oil change would just go up over $11.00 . A close alternative is Mobil 1 0w30 who many say is a thin 30 weight any way .
Good to know, I noticed Autozone only had 5 quart bottles of Mobil 1 0w-30. Going with 0w-20 or 5w-20 means having to buy quart bottles.
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