Just to make sure that I under stand it, a higher VI = less resistance/friction and can mean potentially better MPG. So oils like Sustina and Toyota's could potentially have the best MPG?
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Higher VI = better MPG?
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No, viscosity index isn't deeply connected to gas mileage. HTHS is really a better indicator of the operational viscosity and that's how you can roughly gauge how much thicker it is. Thicker will usually mean lower MPG.
The Toyota 0w20 offers very good gas mileage because it is quite thin with an HTHS of 2.6ish.
The Toyota 0w20 offers very good gas mileage because it is quite thin with an HTHS of 2.6ish.
Not necessarily. A high VI would allow an oil that provides the enough hot viscosity and is thinner at lower temps than another oil with the same hot viscosity but thicker at lower temperatures.
But someone could also chose a high VI oil that is thicker than the engine requires which would not provide a benefit over a lower VI oil that is the appropriate viscosity for the application.
A lower viscosity would provide less resistance and less friction, and a high VI would allow an oil to be at a lower viscosity more of the time.
But someone could also chose a high VI oil that is thicker than the engine requires which would not provide a benefit over a lower VI oil that is the appropriate viscosity for the application.
A lower viscosity would provide less resistance and less friction, and a high VI would allow an oil to be at a lower viscosity more of the time.
Originally Posted By: Mach1Owner
Just to make sure that I under stand it, a higher VI = less resistance/friction
What led to this assumption?
Just to make sure that I under stand it, a higher VI = less resistance/friction
What led to this assumption?
Here's an example:
Mobil 1 0w40 has a VI of 185, and HTHS of 3.8
Red Line 10w60 has a VI of 187, and HTHS of 5.8
Despite having the same VI, the Red Line is nearly 35% thicker under normal use.
Remember that VI can be calculated based on the kinematic viscosity (KV) values, so two oils of vastly different viscosities can have the exact same VI. Don't believe me? Try the calculator for yourself:
http://www.widman.biz/English/Calculators/VI.html
Mobil 1 0w40 has a VI of 185, and HTHS of 3.8
Red Line 10w60 has a VI of 187, and HTHS of 5.8
Despite having the same VI, the Red Line is nearly 35% thicker under normal use.
Remember that VI can be calculated based on the kinematic viscosity (KV) values, so two oils of vastly different viscosities can have the exact same VI. Don't believe me? Try the calculator for yourself:
http://www.widman.biz/English/Calculators/VI.html
^ It could be that 0w show higher VI's than a 5w, hence the misconception.
In general, a shift in weight of oil will show the biggest impact of MPG. E.g. Moving from a 10w30 to 5w30, or 5w30 to 5w20. This is estimated to account for a 1-2% change in MPG. (http://www.fueleconomy.gov/feg/maintain.jsp)
Once you are in the same weight category, you are really splitting hairs on which oil provides better MPG, to the tune of less than 1%. At this point, other aspects of driving, such as acceleration behavior or excess weight can have a larger effect on MPG than oil type. (http://www.fueleconomy.gov/feg/driveHabits.jsp0
In general, a shift in weight of oil will show the biggest impact of MPG. E.g. Moving from a 10w30 to 5w30, or 5w30 to 5w20. This is estimated to account for a 1-2% change in MPG. (http://www.fueleconomy.gov/feg/maintain.jsp)
Once you are in the same weight category, you are really splitting hairs on which oil provides better MPG, to the tune of less than 1%. At this point, other aspects of driving, such as acceleration behavior or excess weight can have a larger effect on MPG than oil type. (http://www.fueleconomy.gov/feg/driveHabits.jsp0
Personally, fuel economy is at the bottom of the list of things that matter to me in an oil. Oil is designed, first and foremost, to protect the engine (via proper lubrication), and I would much rather have a pperfect engine than an extra 1-2 percent increase in economy.
Originally Posted By: Quattro Pete
Originally Posted By: Mach1Owner
Just to make sure that I under stand it, a higher VI = less resistance/friction
What led to this assumption?
There is a school of logic on the board that states (reasonably) that for a given KV100, or HTHS, a higher VI oil will deliver better fuel economy during the period from starting through to hot oil conditions.
The proponents state (unreasonably) that this is the normal state of affairs in engines, and have, in the past attributed 4% additional economy to the effect.
Originally Posted By: Mach1Owner
Just to make sure that I under stand it, a higher VI = less resistance/friction
What led to this assumption?
There is a school of logic on the board that states (reasonably) that for a given KV100, or HTHS, a higher VI oil will deliver better fuel economy during the period from starting through to hot oil conditions.
The proponents state (unreasonably) that this is the normal state of affairs in engines, and have, in the past attributed 4% additional economy to the effect.
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Originally Posted By: Mach1Owner
Just to make sure that I under stand it, a higher VI = less resistance/friction and can mean potentially better MPG. So oils like Sustina and Toyota's could potentially have the best MPG?
The predominate cause for mpg increases in whatever "weight" of oil is the Friction Modifier chemistry in the oil.
Generally speaking, and with all other variables held constant, Fractional gains in MPG can be obtained by lowering the "bulk" viscosity of the oil, so a 0W20 should show a fractional increase in MPG over a 10W40.
Just to make sure that I under stand it, a higher VI = less resistance/friction and can mean potentially better MPG. So oils like Sustina and Toyota's could potentially have the best MPG?
The predominate cause for mpg increases in whatever "weight" of oil is the Friction Modifier chemistry in the oil.
Generally speaking, and with all other variables held constant, Fractional gains in MPG can be obtained by lowering the "bulk" viscosity of the oil, so a 0W20 should show a fractional increase in MPG over a 10W40.
Originally Posted By: Mach1Owner
Just to make sure that I under stand it, a higher VI = less resistance/friction and can mean potentially better MPG. So oils like Sustina and Toyota's could potentially have the best MPG?
Yes, oils like Sustina and TGMO 0W-20s with their 229 and 216 respective viscosity indexes will maximize your fuel economy vs other 0W/5W-20s with much lower VIs although their HTHSVs are nominally the same. That's why these oils were developed in the first place.
The reason is quite simple, they are very much lighter on primarily on start-up but also at normal operating temp's.
Lighter means less friction due to oil drag which translates into improved fuel economy.
Just to make sure that I under stand it, a higher VI = less resistance/friction and can mean potentially better MPG. So oils like Sustina and Toyota's could potentially have the best MPG?
Yes, oils like Sustina and TGMO 0W-20s with their 229 and 216 respective viscosity indexes will maximize your fuel economy vs other 0W/5W-20s with much lower VIs although their HTHSVs are nominally the same. That's why these oils were developed in the first place.
The reason is quite simple, they are very much lighter on primarily on start-up but also at normal operating temp's.
Lighter means less friction due to oil drag which translates into improved fuel economy.
They could yield higher MPG but that increase is probably not noticeable by the average consumer. But over a large number of vehicles sold and driven, it may have some impact. The best advantage is that the oils mentioned by the OP will flow very easily and quickly on cold starts thus protecting the engine for the longer term. That is the real benefit. Increased MPG is a small secondary benefit
Thanks for the correction gents.
Originally Posted By: dparm
Here's an example:
Mobil 1 0w40 has a VI of 185, and HTHS of 3.8
Red Line 10w60 has a VI of 187, and HTHS of 5.8
Despite having the same VI, the Red Line is nearly 35% thicker under normal use.
Remember that VI can be calculated based on the kinematic viscosity (KV) values, so two oils of vastly different viscosities can have the exact same VI. Don't believe me? Try the calculator for yourself:
http://www.widman.biz/English/Calculators/VI.html
Actually RL 10W-60 is about 50% heavier than M1 0W-40 at 150C and M1 0W-40 is 35% lighter.
At 100C RL is over 90% heavier.
Why the disparity? Because the real V.I. of the two oils are quite different with M1 0W-40 being about 18% higher.
When comparing the real V.I. of two oils of different grades you have to take into account the V.I. penalty that applies to lighter oils.
The real V.I. of M1 0W-40 as represented by it's KV40/KV100 ratio is 5.56 meaning as the viscosity drops from 100C to 40C it increases 5.56 times. For RL 10W-60 it increases 6.54 times.
I wrote a post about the subject yesterday:
https://bobistheoilguy.com/forums/posts/3270219/
Here's an example:
Mobil 1 0w40 has a VI of 185, and HTHS of 3.8
Red Line 10w60 has a VI of 187, and HTHS of 5.8
Despite having the same VI, the Red Line is nearly 35% thicker under normal use.
Remember that VI can be calculated based on the kinematic viscosity (KV) values, so two oils of vastly different viscosities can have the exact same VI. Don't believe me? Try the calculator for yourself:
http://www.widman.biz/English/Calculators/VI.html
Actually RL 10W-60 is about 50% heavier than M1 0W-40 at 150C and M1 0W-40 is 35% lighter.
At 100C RL is over 90% heavier.
Why the disparity? Because the real V.I. of the two oils are quite different with M1 0W-40 being about 18% higher.
When comparing the real V.I. of two oils of different grades you have to take into account the V.I. penalty that applies to lighter oils.
The real V.I. of M1 0W-40 as represented by it's KV40/KV100 ratio is 5.56 meaning as the viscosity drops from 100C to 40C it increases 5.56 times. For RL 10W-60 it increases 6.54 times.
I wrote a post about the subject yesterday:
https://bobistheoilguy.com/forums/posts/3270219/
What leads you to believe that use of thinner oils will lead to less than perfect engines?
Originally Posted By: nleksan
Personally, fuel economy is at the bottom of the list of things that matter to me in an oil. Oil is designed, first and foremost, to protect the engine (via proper lubrication), and I would much rather have a perfect engine than an extra 1-2 percent increase in economy.
Originally Posted By: nleksan
Personally, fuel economy is at the bottom of the list of things that matter to me in an oil. Oil is designed, first and foremost, to protect the engine (via proper lubrication), and I would much rather have a perfect engine than an extra 1-2 percent increase in economy.
Originally Posted By: nleksan
Personally, fuel economy is at the bottom of the list of things that matter to me in an oil. Oil is designed, first and foremost, to protect the engine (via proper lubrication), and I would much rather have a pperfect engine than an extra 1-2 percent increase in economy.
Considering most people in the general public drive their vehicles these days with unchecked tire pressure,dirty air filters,etc the increase in gas mileage can be found elsewhere.
Personally, fuel economy is at the bottom of the list of things that matter to me in an oil. Oil is designed, first and foremost, to protect the engine (via proper lubrication), and I would much rather have a pperfect engine than an extra 1-2 percent increase in economy.
Considering most people in the general public drive their vehicles these days with unchecked tire pressure,dirty air filters,etc the increase in gas mileage can be found elsewhere.
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