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Old 12-06-2018, 08:36 AM   #1 (permalink)
Daox
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Redline MT-LV 70W/75W gear oil for 5 speed manual Mirage (OE is 75W80)

I was poking around today looking at different gear oils. The 2014+ Mirage calls for a 75W80 gear oil. The 75W is the engine viscosity when cold, and the 80 is the viscosity when its hot. All oil is substantially thicker when cold, so getting a low first number is a good thing as it will always be thinner when hot. You just don't want it to get too thin, or you can accelerate wear in your transmission. Here is a chart to help illustrate things.





Therefore, I was looking to see if I could get a 70W80 or even 65W80. Alas, I can not find anything like that. However, what I did find was Redline MT-LV 70W/75W. You'll notice this doesn't follow the normal naming convention. So, I'm not exactly sure what to think about it. It is quite a bit thinner than Redline MTL 75W80 that many here have used.



Here are the viscosity specs of the two:

75W/80 (OE spec)
Vis @ 100C, CSt 10.2
Vis @ 40C, CSt 50

70W/75W
Vis @ 100C, CSt 6.5
Vis @ 40C, CSt 9.8


For reference, 40C is 104F. That already seems warm for a manual transmission, but I haven't measured my transmission's temperature. Anyway, at 104F, you can see the 70W/75W is 5 times thinner than the 75W80 oil. Thats a heck of a lot less churning going on. Less churning means more power and efficiency.

Anyways, I post this info because I am thinking about using it in the Mirage. I have contacted Blackstone Labs, a third party oil analysis company. I've asked them how they recommend I proceed with testing this oil with minimal risk to my transmission. I've used them many times in the past for engine oil analysis and they're very helpful.

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