Shannow thanks for the charts and discussion.....this is very interesting.
Sources of engine heat and effects of oil viscosity
- Thread starter OilUzer
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This whole thick/thin thing is way to "emotional" ... Folks are making oil decisions based on a "feeling" that it will do XYZ ... It's like brand loyalty - fan boys/girls.
What does the engine want? It's based on actual bearing numbers (clearances, wear, operating environment), piston to wall clearances, and type of valve train. If you live in Minnesota it can be one thing. If you live in San Diego, it can be another.
% heat generated by increased viscosity is somewhat pertinent to operating environment, but offset by HTHS capability.
It's all about keeping the metal bits from actually touching in the operating range under the loads that are being experienced. If a NASCAR engine could live on 0W-20, those guys would have made the switch years ago. Drag Racers are trying to live with "light oils" as they know it means less drag ("free HP"), but they are paying a steep price to learn how.
Almost all engines are actually designed around the equivalent of SAE 30. BMW have tried to tighten bearing clearances to allow constant use of thinner oils, ditto Audi. But in both cases it has not been an overwhelming success. Fine for mom chasing the kids and doing in-town errands. But falls on its face when pushed hard for hours on end like cruising across the US western deserts at elevated speeds with the AC on. Which is why all the makes have some caveat somewhere to use heavier oil on track days, etc. It's about the Operating Environment ...
What does the engine want? It's based on actual bearing numbers (clearances, wear, operating environment), piston to wall clearances, and type of valve train. If you live in Minnesota it can be one thing. If you live in San Diego, it can be another.
% heat generated by increased viscosity is somewhat pertinent to operating environment, but offset by HTHS capability.
It's all about keeping the metal bits from actually touching in the operating range under the loads that are being experienced. If a NASCAR engine could live on 0W-20, those guys would have made the switch years ago. Drag Racers are trying to live with "light oils" as they know it means less drag ("free HP"), but they are paying a steep price to learn how.
Almost all engines are actually designed around the equivalent of SAE 30. BMW have tried to tighten bearing clearances to allow constant use of thinner oils, ditto Audi. But in both cases it has not been an overwhelming success. Fine for mom chasing the kids and doing in-town errands. But falls on its face when pushed hard for hours on end like cruising across the US western deserts at elevated speeds with the AC on. Which is why all the makes have some caveat somewhere to use heavier oil on track days, etc. It's about the Operating Environment ...
Originally Posted by Shannow
Originally Posted by ZeeOSix
Dang Shannow ... your first post has all kinds of "scary" graphs and tables.
Halloween is coming...wanted to get into practice before scary clown day.
Hang onto your breeches, as here's a paper as well...
https://www.researchgate.net/public...e_problem_causes_and_potential_solutions
I understand they reduce grown men to quivering messes.
That is an in depth analysis. A lot to digest. Thanks for posting.
Originally Posted by ZeeOSix
Dang Shannow ... your first post has all kinds of "scary" graphs and tables.
Halloween is coming...wanted to get into practice before scary clown day.
Hang onto your breeches, as here's a paper as well...
https://www.researchgate.net/public...e_problem_causes_and_potential_solutions
I understand they reduce grown men to quivering messes.
That is an in depth analysis. A lot to digest. Thanks for posting.
Originally Posted by BrocLuno
This whole thick/thin thing is way to "emotional" ... Folks are making oil decisions based on a "feeling" that it will do XYZ ... It's like brand loyalty - fan boys/girls.
What does the engine want? It's based on actual bearing numbers (clearances, wear, operating environment), piston to wall clearances, and type of valve train. If you live in Minnesota it can be one thing. If you live in San Diego, it can be another.
% heat generated by increased viscosity is somewhat pertinent to operating environment, but offset by HTHS capability.
It's all about keeping the metal bits from actually touching in the operating range under the loads that are being experienced. If a NASCAR engine could live on 0W-20, those guys would have made the switch years ago. Drag Racers are trying to live with "light oils" as they know it means less drag ("free HP"), but they are paying a steep price to learn how.
Almost all engines are actually designed around the equivalent of SAE 30. BMW have tried to tighten bearing clearances to allow constant use of thinner oils, ditto Audi. But in both cases it has not been an overwhelming success. Fine for mom chasing the kids and doing in-town errands. But falls on its face when pushed hard for hours on end like cruising across the US western deserts at elevated speeds with the AC on. Which is why all the makes have some caveat somewhere to use heavier oil on track days, etc. It's about the Operating Environment ...
Thank you for this excellent comment BrocLuno. This should be nominated for comment of the year.
This whole thick/thin thing is way to "emotional" ... Folks are making oil decisions based on a "feeling" that it will do XYZ ... It's like brand loyalty - fan boys/girls.
What does the engine want? It's based on actual bearing numbers (clearances, wear, operating environment), piston to wall clearances, and type of valve train. If you live in Minnesota it can be one thing. If you live in San Diego, it can be another.
% heat generated by increased viscosity is somewhat pertinent to operating environment, but offset by HTHS capability.
It's all about keeping the metal bits from actually touching in the operating range under the loads that are being experienced. If a NASCAR engine could live on 0W-20, those guys would have made the switch years ago. Drag Racers are trying to live with "light oils" as they know it means less drag ("free HP"), but they are paying a steep price to learn how.
Almost all engines are actually designed around the equivalent of SAE 30. BMW have tried to tighten bearing clearances to allow constant use of thinner oils, ditto Audi. But in both cases it has not been an overwhelming success. Fine for mom chasing the kids and doing in-town errands. But falls on its face when pushed hard for hours on end like cruising across the US western deserts at elevated speeds with the AC on. Which is why all the makes have some caveat somewhere to use heavier oil on track days, etc. It's about the Operating Environment ...
Thank you for this excellent comment BrocLuno. This should be nominated for comment of the year.
Originally Posted by BrocLuno
It's all about keeping the metal bits from actually touching in the operating range under the loads that are being experienced. If a NASCAR engine could live on 0W-20, those guys would have made the switch years ago. Drag Racers are trying to live with "light oils" as they know it means less drag ("free HP"), but they are paying a steep price to learn how.
according to https://www.motorstate.com/oilviscosity.htm, NASCAR is already running 20WT oil.
Quote
Look at an NHRA Pro Stock engine, a NASCAR Sprint Cup engine and a World of Outlaws 410 Sprint engine. Each engine has a very different operating oil temperature - Pro Stock, 100°F; NASCAR, 220°F and sprint cars, 300°F. All three engines run very different viscosity oils as well − SAE 0W-5, SAE 5W-20 and SAE 15W-50.
It's all about keeping the metal bits from actually touching in the operating range under the loads that are being experienced. If a NASCAR engine could live on 0W-20, those guys would have made the switch years ago. Drag Racers are trying to live with "light oils" as they know it means less drag ("free HP"), but they are paying a steep price to learn how.
according to https://www.motorstate.com/oilviscosity.htm, NASCAR is already running 20WT oil.
Quote
Look at an NHRA Pro Stock engine, a NASCAR Sprint Cup engine and a World of Outlaws 410 Sprint engine. Each engine has a very different operating oil temperature - Pro Stock, 100°F; NASCAR, 220°F and sprint cars, 300°F. All three engines run very different viscosity oils as well − SAE 0W-5, SAE 5W-20 and SAE 15W-50.
Originally Posted by thescreensavers
Quote
Look at an NHRA Pro Stock engine, a NASCAR Sprint Cup engine and a World of Outlaws 410 Sprint engine. Each engine has a very different operating oil temperature - Pro Stock, 100°F; NASCAR, 220°F and sprint cars, 300°F. All three engines run very different viscosity oils as well − SAE 0W-5, SAE 5W-20 and SAE 15W-50.
Are the sprint cars air cooled?
Quote
Look at an NHRA Pro Stock engine, a NASCAR Sprint Cup engine and a World of Outlaws 410 Sprint engine. Each engine has a very different operating oil temperature - Pro Stock, 100°F; NASCAR, 220°F and sprint cars, 300°F. All three engines run very different viscosity oils as well − SAE 0W-5, SAE 5W-20 and SAE 15W-50.
Are the sprint cars air cooled?
MolaKule
Staff member
Originally Posted by OilUzer
in general, what % of engine heat is generated by viscous shearing, combustion or friction? Anything else terminology wise? Is viscous shearing a component of friction which is causing the heat, and heating up the oil which is heating the block ...
I always thought that most of the engine heat is from combustion ... viscous shearing was mentioned in one the recent threads on this forum and made me wonder about the percentages....
Shannow's excellent references explains the energy distribution in technical detail.
Let's get back to energy and thermodynamic basics for a moment.
I like to think in terms of energy conversions in this regard.
Potential Chemical energy from the fuel (via combustion) is converted to thermal and mechanical energy.
A majority of the chemical energy converted to thermal energy is blown out as hot exhaust gasses (fluid dynamics).
Some of that thermal energy is converted to do actual mechanical work. That mechanical energy facilitates rotational motion in the form of torque.
Some of the mechanical sliding and rotational energy shears the lubricant because it has viscosity and viscosity tends to resist shearing. Some of the mechanical energy (oil pump) energy is also used to raise the pressure of the lubricant in the system for distribution. Overcoming ANY resistive force requires energy to overcome that resistive force.
The Mechanical action of shearing the oil or moving the oil is converted back to thermal energy which raises the temperature of the oil.
In general, higher fluid viscosity means more mechanical energy is used to shear and force the oil throughout the system. This raises the overall temperature of the bulk oil.
I hope this helps.
in general, what % of engine heat is generated by viscous shearing, combustion or friction? Anything else terminology wise? Is viscous shearing a component of friction which is causing the heat, and heating up the oil which is heating the block ...
I always thought that most of the engine heat is from combustion ... viscous shearing was mentioned in one the recent threads on this forum and made me wonder about the percentages....
Shannow's excellent references explains the energy distribution in technical detail.
Let's get back to energy and thermodynamic basics for a moment.
I like to think in terms of energy conversions in this regard.
Potential Chemical energy from the fuel (via combustion) is converted to thermal and mechanical energy.
A majority of the chemical energy converted to thermal energy is blown out as hot exhaust gasses (fluid dynamics).
Some of that thermal energy is converted to do actual mechanical work. That mechanical energy facilitates rotational motion in the form of torque.
Some of the mechanical sliding and rotational energy shears the lubricant because it has viscosity and viscosity tends to resist shearing. Some of the mechanical energy (oil pump) energy is also used to raise the pressure of the lubricant in the system for distribution. Overcoming ANY resistive force requires energy to overcome that resistive force.
The Mechanical action of shearing the oil or moving the oil is converted back to thermal energy which raises the temperature of the oil.
In general, higher fluid viscosity means more mechanical energy is used to shear and force the oil throughout the system. This raises the overall temperature of the bulk oil.
I hope this helps.
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It's threads like this and others like it, no matter the subject, that make this the best forum site I've yet to find. Thanks to all those members who take the time and effort to share their knowledge and experience!
Originally Posted by MolaKule
Originally Posted by OilUzer
in general, what % of engine heat is generated by viscous shearing, combustion or friction? Anything else terminology wise? Is viscous shearing a component of friction which is causing the heat, and heating up the oil which is heating the block ...
I always thought that most of the engine heat is from combustion ... viscous shearing was mentioned in one the recent threads on this forum and made me wonder about the percentages....
Shannow's excellent references explains the energy distribution in technical detail.
Let's get back to energy and thermodynamic basics for a moment.
I like to think in terms of energy conversions in this regard.
Potential Chemical energy from the fuel (via combustion) is converted to thermal and mechanical energy.
A majority of the chemical energy converted to thermal energy is blown out as hot exhaust gasses (fluid dynamics).
Some of that thermal energy is converted to do actual mechanical work. That mechanical energy facilitates rotational motion in the form of torque.
Some of the mechanical sliding and rotational energy shears the lubricant because it has viscosity and viscosity tends to resist shearing. Some of the mechanical energy (oil pump) energy is also used to raise the pressure of the lubricant in the system for distribution. Overcoming ANY resistive force requires energy to overcome that resistive force.
The Mechanical action of shearing the oil or moving the oil is converted back to thermal energy which raises the temperature of the oil.
In general, higher fluid viscosity means more mechanical energy is used to shear and force the oil throughout the system. This raises the overall temperature of the bulk oil.
I hope this helps.
Thank you very much for putting it in words!
l have to get on my pc to be able to review/see Shannow's chart better and I'm not taking any credit away from his chart explanation!
your response answered one of my questions and misunderstanding regarding the main source of oil temperature. I thought the chemical energy in cylinder head (i.e. the controlled explosion
) is the main cause of oil temperature rise but as you put it the "majority" of that energy is "blown out as hot gases". Therefore not a major contributor to oil temperature rise. That also answers my other question re "oil carrying more heat from combustion ..." If the main cause/source of heat (in oil) is internal ( e.g. friction, shearing, etc.), heat transfer from cylinder head is insignificant. Hope I'm not oversimplifying it
Originally Posted by OilUzer
in general, what % of engine heat is generated by viscous shearing, combustion or friction? Anything else terminology wise? Is viscous shearing a component of friction which is causing the heat, and heating up the oil which is heating the block ...
I always thought that most of the engine heat is from combustion ... viscous shearing was mentioned in one the recent threads on this forum and made me wonder about the percentages....
Shannow's excellent references explains the energy distribution in technical detail.
Let's get back to energy and thermodynamic basics for a moment.
I like to think in terms of energy conversions in this regard.
Potential Chemical energy from the fuel (via combustion) is converted to thermal and mechanical energy.
A majority of the chemical energy converted to thermal energy is blown out as hot exhaust gasses (fluid dynamics).
Some of that thermal energy is converted to do actual mechanical work. That mechanical energy facilitates rotational motion in the form of torque.
Some of the mechanical sliding and rotational energy shears the lubricant because it has viscosity and viscosity tends to resist shearing. Some of the mechanical energy (oil pump) energy is also used to raise the pressure of the lubricant in the system for distribution. Overcoming ANY resistive force requires energy to overcome that resistive force.
The Mechanical action of shearing the oil or moving the oil is converted back to thermal energy which raises the temperature of the oil.
In general, higher fluid viscosity means more mechanical energy is used to shear and force the oil throughout the system. This raises the overall temperature of the bulk oil.
I hope this helps.
Thank you very much for putting it in words!
l have to get on my pc to be able to review/see Shannow's chart better and I'm not taking any credit away from his chart explanation!
your response answered one of my questions and misunderstanding regarding the main source of oil temperature. I thought the chemical energy in cylinder head (i.e. the controlled explosion
No offense to anyone, (the charts are actually impressive!) but IN REALITY what does it really matter where the heat comes from? Other than making interesting reading, many of the questions voiced here are by and large not applicable to 99+% of drivers. One guy even wanted to know how much the weight savings on running a smaller tire would affect his acceleration.
Long story short, run a quality oil and filter for a reasonable interval, and you will give your vehicle as much lube care as it will ever need.
Long story short, run a quality oil and filter for a reasonable interval, and you will give your vehicle as much lube care as it will ever need.
One would wonder then what those people who it doesn't apply to are doing on bobistheoilguy as a technical forum.
They'd be much better on lookinyourmanual.com which would answer their 99th percentile issues.
Nobody is making anybody read the technical forums.
They'd be much better on lookinyourmanual.com which would answer their 99th percentile issues.
Nobody is making anybody read the technical forums.
Originally Posted by OilUzer
Thank you very much for putting it in words!
l have to get on my pc to be able to review/see Shannow's chart better and I'm not taking any credit away from his chart explanation!
your response answered one of my questions and misunderstanding regarding the main source of oil temperature. I thought the chemical energy in cylinder head (i.e. the controlled explosion
) is the main cause of oil temperature rise but as you put it the "majority" of that energy is "blown out as hot gases". Therefore not a major contributor to oil temperature rise. That also answers my other question re "oil carrying more heat from combustion ..." If the main cause/source of heat (in oil) is internal ( e.g. friction, shearing, etc.), heat transfer from cylinder head is insignificant. Hope I'm not oversimplifying it
Here's something that might help (it's a picture again sorry). Many of the papers that I've read discount the piston/skirt shear as the heat generated goes straight into the coolant, rather than splashing back into the sump. That's shown here in the piston friction loop heading back into the coolant loop.
Thank you very much for putting it in words!
l have to get on my pc to be able to review/see Shannow's chart better and I'm not taking any credit away from his chart explanation!
your response answered one of my questions and misunderstanding regarding the main source of oil temperature. I thought the chemical energy in cylinder head (i.e. the controlled explosion
Here's something that might help (it's a picture again sorry). Many of the papers that I've read discount the piston/skirt shear as the heat generated goes straight into the coolant, rather than splashing back into the sump. That's shown here in the piston friction loop heading back into the coolant loop.
Will try another demonstration using the big end flows...
Take the big end for example...
* 2.38ml/sec oil flow
* 51W heat generation within the bearing
* 147C exit temperature (taking the shell temperature).
For the exercise, we'll assume that ALL of the oil that leaves the bearing as it passes TDC strikes the piston crown and is heated to 250C (ring belt temperarture).
1.19ml/sec, 1 g/sec roughly, 100C temperature rise.
That scenario would add 167W to the oil...versus the 245W due to friction (148W+97W)
But clearly, not all the oil on the TDC swing hits the piston, most of it hits the walls, transferring the 147C temperature to the jackets, and being cooled a bit before returning to the sump.
Take the big end for example...
* 2.38ml/sec oil flow
* 51W heat generation within the bearing
* 147C exit temperature (taking the shell temperature).
For the exercise, we'll assume that ALL of the oil that leaves the bearing as it passes TDC strikes the piston crown and is heated to 250C (ring belt temperarture).
1.19ml/sec, 1 g/sec roughly, 100C temperature rise.
That scenario would add 167W to the oil...versus the 245W due to friction (148W+97W)
But clearly, not all the oil on the TDC swing hits the piston, most of it hits the walls, transferring the 147C temperature to the jackets, and being cooled a bit before returning to the sump.
Originally Posted by Shannow
(it's a picture again sorry).
Lots of words don't work for me...love pictures and graphs.
(it's a picture again sorry).
Lots of words don't work for me...love pictures and graphs.
Originally Posted by gfh77665
No offense to anyone, (the charts are actually impressive!) but IN REALITY what does it really matter where the heat comes from?
It certainly would to engineers designing engines.
No offense to anyone, (the charts are actually impressive!) but IN REALITY what does it really matter where the heat comes from?
It certainly would to engineers designing engines.
Originally Posted by Shannow
Will try another demonstration using the big end flows...
Take the big end for example...
* 2.38ml/sec oil flow
* 51W heat generation within the bearing
* 147C exit temperature (taking the shell temperature).
For the exercise, we'll assume that ALL of the oil that leaves the bearing as it passes TDC strikes the piston crown and is heated to 250C (ring belt temperarture).
1.19ml/sec, 1 g/sec roughly, 100C temperature rise.
That scenario would add 167W to the oil...versus the 245W due to friction (148W+97W)
But clearly, not all the oil on the TDC swing hits the piston, most of it hits the walls, transferring the 147C temperature to the jackets, and being cooled a bit before returning to the sump.
A lot of friction reduction is being engineered into engines nowadays. For example, I've read where the SkyActiv engines do not fire at TDC but on the downstroke. Then there are coatings, special machining, etc. Reduction of friction means less heat as well.
Will try another demonstration using the big end flows...
Take the big end for example...
* 2.38ml/sec oil flow
* 51W heat generation within the bearing
* 147C exit temperature (taking the shell temperature).
For the exercise, we'll assume that ALL of the oil that leaves the bearing as it passes TDC strikes the piston crown and is heated to 250C (ring belt temperarture).
1.19ml/sec, 1 g/sec roughly, 100C temperature rise.
That scenario would add 167W to the oil...versus the 245W due to friction (148W+97W)
But clearly, not all the oil on the TDC swing hits the piston, most of it hits the walls, transferring the 147C temperature to the jackets, and being cooled a bit before returning to the sump.
A lot of friction reduction is being engineered into engines nowadays. For example, I've read where the SkyActiv engines do not fire at TDC but on the downstroke. Then there are coatings, special machining, etc. Reduction of friction means less heat as well.
Originally Posted by PimTac
... I've read where the SkyActiv engines do not fire at TDC but on the downstroke. ... Reduction of friction means less heat as well.
Why would retarded ignition timing improve overall efficiency in their case, when it normally doesn't? It seems that would imply extraordinarily fast flame front speed, or some other way to combust all the mixture nearly simultaneously.
... I've read where the SkyActiv engines do not fire at TDC but on the downstroke. ... Reduction of friction means less heat as well.
Why would retarded ignition timing improve overall efficiency in their case, when it normally doesn't? It seems that would imply extraordinarily fast flame front speed, or some other way to combust all the mixture nearly simultaneously.
Originally Posted by Shannow
One would wonder then what those people who it doesn't apply to are doing on bobistheoilguy as a technical forum.
They'd be much better on lookinyourmanual.com which would answer their 99th percentile issues.
Nobody is making anybody read the technical forums.
That's what I was going to say. Thank you for all of the great information.
One would wonder then what those people who it doesn't apply to are doing on bobistheoilguy as a technical forum.
They'd be much better on lookinyourmanual.com which would answer their 99th percentile issues.
Nobody is making anybody read the technical forums.
That's what I was going to say. Thank you for all of the great information.
Very Interesting and reassuring that as long as cooling capacity is not exceeded, oil temperature will quickly come down towards coolant temp when rpms drop in water cooled reciprocating engines.
Originally Posted by Shannow
Will try another demonstration using the big end flows...
Take the big end for example...
* 2.38ml/sec oil flow
* 51W heat generation within the bearing
* 147C exit temperature (taking the shell temperature).
For the exercise, we'll assume that ALL of the oil that leaves the bearing as it passes TDC strikes the piston crown and is heated to 250C (ring belt temperarture).
1.19ml/sec, 1 g/sec roughly, 100C temperature rise.
That scenario would add 167W to the oil...versus the 245W due to friction (148W+97W)
But clearly, not all the oil on the TDC swing hits the piston, most of it hits the walls, transferring the 147C temperature to the jackets, and being cooled a bit before returning to the sump.
Originally Posted by Shannow
Will try another demonstration using the big end flows...
Take the big end for example...
* 2.38ml/sec oil flow
* 51W heat generation within the bearing
* 147C exit temperature (taking the shell temperature).
For the exercise, we'll assume that ALL of the oil that leaves the bearing as it passes TDC strikes the piston crown and is heated to 250C (ring belt temperarture).
1.19ml/sec, 1 g/sec roughly, 100C temperature rise.
That scenario would add 167W to the oil...versus the 245W due to friction (148W+97W)
But clearly, not all the oil on the TDC swing hits the piston, most of it hits the walls, transferring the 147C temperature to the jackets, and being cooled a bit before returning to the sump.
Originally Posted by Bryanccfshr
Very Interesting and reassuring that as long as cooling capacity is not exceeded, oil temperature will quickly come down towards coolant temp when rpms drop in water cooled reciprocating engines.
Originally Posted by Shannow
Will try another demonstration using the big end flows...
Take the big end for example...
* 2.38ml/sec oil flow
* 51W heat generation within the bearing
* 147C exit temperature (taking the shell temperature).
For the exercise, we'll assume that ALL of the oil that leaves the bearing as it passes TDC strikes the piston crown and is heated to 250C (ring belt temperarture).
1.19ml/sec, 1 g/sec roughly, 100C temperature rise.
That scenario would add 167W to the oil...versus the 245W due to friction (148W+97W)
But clearly, not all the oil on the TDC swing hits the piston, most of it hits the walls, transferring the 147C temperature to the jackets, and being cooled a bit before returning to the sump.
Really good point...
And Shannow great post and pictures are very helpful as well.
Qucik question... Do you really work in Mentone?? That is in the least populated county in the lower 48... Loving county.. That is quite aways from Galveston... Needless to say
Very Interesting and reassuring that as long as cooling capacity is not exceeded, oil temperature will quickly come down towards coolant temp when rpms drop in water cooled reciprocating engines.
Originally Posted by Shannow
Will try another demonstration using the big end flows...
Take the big end for example...
* 2.38ml/sec oil flow
* 51W heat generation within the bearing
* 147C exit temperature (taking the shell temperature).
For the exercise, we'll assume that ALL of the oil that leaves the bearing as it passes TDC strikes the piston crown and is heated to 250C (ring belt temperarture).
1.19ml/sec, 1 g/sec roughly, 100C temperature rise.
That scenario would add 167W to the oil...versus the 245W due to friction (148W+97W)
But clearly, not all the oil on the TDC swing hits the piston, most of it hits the walls, transferring the 147C temperature to the jackets, and being cooled a bit before returning to the sump.
Really good point...
And Shannow great post and pictures are very helpful as well.
Qucik question... Do you really work in Mentone?? That is in the least populated county in the lower 48... Loving county.. That is quite aways from Galveston... Needless to say
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