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Old 07-27-2017, 12:23 PM   #34 (permalink)
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Originally Posted by diesel_john View Post
What are the pros and cons between hot thick oil and cool thin oil like john deere hy-gard?
No difference other than the additives of the oil and energy is required to heat oil.
What the goal is here is to thin the oil so there is less resistance inside the transmission.
Most if not all 90's mazda manual transmissions speced ATF from the factory. Thats what was put in them and on the cheaper cars like mine it often was never changed. There are manual transmissions in festivas that have gone 300k miles just fine on ATF.
So, amsoil has an equivilant of honda mtf. They post the viscosity specs. Same with their synthetic ATF.
MTF is thicker than 0w20 but thinner than 0w30 engine oil. ATF is thinner than both.
I put the numbers into a viscosity calculator. Lets say you managed to get your mtf up to 195f on a long drive. ATF would be the same viscosity 37 degrees lower at 158f.

With my small car towing a big trailer in 86f when my coolant overheated the transmission case was 155f. The oil was probably not as hot because the trans shell would have been hotter from the rad fan blowing 220f air directly onto it.
Normal driving is 120f iirc.
Lets say where you live is hotter and your transmission gets to 130f naturally on a long drive when its hot out. Atf would be at the same viscosity 25f lower at 104f.
We usually commute when its cooler and i dont know how cold your area gets in the winter, but mtf at 77f is the same as atf at 61f.
Atf is just as thin at 21f as mtf at 32f (11f colder)
Atf is just as thin at 6f as mtf at 14f.

So i hope you can record the demterature difference this jacket makes on your oil. If it doesnt heat it up quickly perhaps consider using a thinner oil to begin with.

*edit* my point with all this which i forgot to mention is that on a 7 mile drive starting with thinner oil like this will likely make more of a difference than trying to heat it through the transmission case.

Last edited by dancam; 07-27-2017 at 12:37 PM..
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