Cold Weather Gear Changes
02-27-2013, 07:45 AM
#1
Registered User
Thread Starter
Cold Weather Gear Changes
Hi all,
Around this time of year we get quite a few questions about experiencing difficult gearshifts in cold weather, so we thought you might find this useful.
Using the incorrect viscosity gear oil in your car can make gear changes very difficult when the gearbox, and oil are cold. This is why we often don't recommend using thicker gear oils than the manufacturer specifies. It is easy to think that increasing the viscosity from a 75w-80 to 75w-90 or 75w-90 to 75w-140 isn't going to affect the cold properties of the oil, but it does.
Below are some figures showing the viscosity of a selection of oils at 40C measured in mm²/s ( 1 millimeter²/second = 1 centistoke, A centistoke is a decimal fraction of the CGS unit of kinematic viscosity stokes, which is equal to centimeter per second (cm²/s). 1 stokes is a kinematic viscosity of a fluid with a density of 1 g/cm³ and a dynamic viscosity of 1 poise… In short the thickness of oil!). 40degc may not seem cold but this is the temperature at which the viscosity is measured and is the information you will find on the oil technical data sheets.
I have listed specific brands and products to make it easier to see the differences in viscosity.
Fuchs Sintofluid FE 75w = 40.8 @ 40°c
Fuchs Sintofluid 75w-80 = 49.8 @ 40°c
Fuchs Sintopoid 75w-90 = 90.5 @ 40°c
Fuchs Sintopoid LS 75w140 = 170 @ 40°c
As you can see from that, they are all 75w oils, but there is a large difference in the viscosity at lower temps; the Sintopoid 75w-90 is over twice as thick as the Sintofluid FE 75w when cold and the 75w-140 is almost twice as thick as the 75w-90.
So, if you've got a car that needs one grade of oil as standard, but you've modified it and decide to try a thicker oil, or someone puts the wrong oil in, it might really affect the cold gear shifts. Usually, increasing the quality is a better option than increasing the viscosity when thinking about upgrading from standard fluid.
Also, viscosity ratings are not exact points, but are a band that the viscosity should fall in. The Motul Gear 300 75w-90 has a viscosity of 76.2mm²/s at 40°c and the Castrol Universal 75w-90 is 84.8mm²/s, so you can see there is some variation in oils that appear to be the same viscosity.
A lot of gearboxes specify an 80w-90 rather than a 75w-90, but I would always tend to go for a 75w-90 instead as there can be a large difference is the viscosity when cold. The Motul Gearbox 80w-90 is 164mm²/s, so over twice as thick as their Gear 300 when cold. If you're using an 80w-90 and are having stiff cold gear changes, changing to a 75w-90 is likely to improve things.
If you have any questions or need further advice please post here or email us at sales@opieoils.co.uk
Cheers
Tim.
Around this time of year we get quite a few questions about experiencing difficult gearshifts in cold weather, so we thought you might find this useful.
Using the incorrect viscosity gear oil in your car can make gear changes very difficult when the gearbox, and oil are cold. This is why we often don't recommend using thicker gear oils than the manufacturer specifies. It is easy to think that increasing the viscosity from a 75w-80 to 75w-90 or 75w-90 to 75w-140 isn't going to affect the cold properties of the oil, but it does.
Below are some figures showing the viscosity of a selection of oils at 40C measured in mm²/s ( 1 millimeter²/second = 1 centistoke, A centistoke is a decimal fraction of the CGS unit of kinematic viscosity stokes, which is equal to centimeter per second (cm²/s). 1 stokes is a kinematic viscosity of a fluid with a density of 1 g/cm³ and a dynamic viscosity of 1 poise… In short the thickness of oil!). 40degc may not seem cold but this is the temperature at which the viscosity is measured and is the information you will find on the oil technical data sheets.
I have listed specific brands and products to make it easier to see the differences in viscosity.
Fuchs Sintofluid FE 75w = 40.8 @ 40°c
Fuchs Sintofluid 75w-80 = 49.8 @ 40°c
Fuchs Sintopoid 75w-90 = 90.5 @ 40°c
Fuchs Sintopoid LS 75w140 = 170 @ 40°c
As you can see from that, they are all 75w oils, but there is a large difference in the viscosity at lower temps; the Sintopoid 75w-90 is over twice as thick as the Sintofluid FE 75w when cold and the 75w-140 is almost twice as thick as the 75w-90.
So, if you've got a car that needs one grade of oil as standard, but you've modified it and decide to try a thicker oil, or someone puts the wrong oil in, it might really affect the cold gear shifts. Usually, increasing the quality is a better option than increasing the viscosity when thinking about upgrading from standard fluid.
Also, viscosity ratings are not exact points, but are a band that the viscosity should fall in. The Motul Gear 300 75w-90 has a viscosity of 76.2mm²/s at 40°c and the Castrol Universal 75w-90 is 84.8mm²/s, so you can see there is some variation in oils that appear to be the same viscosity.
A lot of gearboxes specify an 80w-90 rather than a 75w-90, but I would always tend to go for a 75w-90 instead as there can be a large difference is the viscosity when cold. The Motul Gearbox 80w-90 is 164mm²/s, so over twice as thick as their Gear 300 when cold. If you're using an 80w-90 and are having stiff cold gear changes, changing to a 75w-90 is likely to improve things.
If you have any questions or need further advice please post here or email us at sales@opieoils.co.uk
Cheers
Tim.
02-27-2013, 02:00 PM
#3
Registered User
More importantly. What did Honda spec when they were part of the co development of the MTF gearbox oils
This is also the reason why sticking with the proper oils is good for gearbox and changes. My box is 149k and always ran on Honda MTF. No issues with cold selection, if there are issues then a fresh oil usually helps too
How an oil flows in a tube at 40C under gravity isn't the only thing to consider. A 75W-140 can be thinner than a 75W-90 if you compare purely the base oil viscosity.
This is also the reason why sticking with the proper oils is good for gearbox and changes. My box is 149k and always ran on Honda MTF. No issues with cold selection, if there are issues then a fresh oil usually helps too
How an oil flows in a tube at 40C under gravity isn't the only thing to consider. A 75W-140 can be thinner than a 75W-90 if you compare purely the base oil viscosity.
02-28-2013, 06:38 AM
#5
Registered User
Thread Starter
More importantly. What did Honda spec when they were part of the co development of the MTF gearbox oils
This is also the reason why sticking with the proper oils is good for gearbox and changes. My box is 149k and always ran on Honda MTF. No issues with cold selection, if there are issues then a fresh oil usually helps too
How an oil flows in a tube at 40C under gravity isn't the only thing to consider. A 75W-140 can be thinner than a 75W-90 if you compare purely the base oil viscosity.
This is also the reason why sticking with the proper oils is good for gearbox and changes. My box is 149k and always ran on Honda MTF. No issues with cold selection, if there are issues then a fresh oil usually helps too
How an oil flows in a tube at 40C under gravity isn't the only thing to consider. A 75W-140 can be thinner than a 75W-90 if you compare purely the base oil viscosity.
Cheers
Tim
03-01-2013, 08:16 AM
#7
Registered User
Thread Starter
I don't have the details of the additives used in the MTFIII and yes, the additives will affect the shift. All I can really say on that is that several people that have gone from Honda MTF to Amsoil, Redline or Fuchs have said that the shift feel has improved.Others reckon the Honda stuff feels the best, it's down to opinion I guess.
Cheers
Tim
Cheers
Tim
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