Safe to switch from SAE 80 to 75W-80?

LeoStrop

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If it wasn't so expensive i would get some Redline MTL 75W-80, it even states on the website it is recommended as a replacement for SAE 80, with the Monograde 80 it's true that the shifting is a little notchy when cold, but perfect once the oil has warmed up a bit.

It would be a great choice, but since it's that expensive, making the change for a typical 75W-80/85 full synthetic will already be a nice jump compared to the SAE 80. You will be going from a VI of ~100 to ~160
 

FCD

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It would be a great choice, but since it's that expensive, making the change for a typical 75W-80/85 full synthetic will already be a nice jump compared to the SAE 80. You will be going from a VI of ~100 to ~160
I put a used transmission in the Capri last august as the original one was pretty tired after over 300k miles.
I put in Castrol SAE 80 and it works great but i might change it as it only takes 1.9L and has an easily accesible drain plug, one oil i have looked at as an alternative is Ravenol MTF-2 75W-80 , expensive but still half the price of Redline, supposedly it's PAO based which sounds good.
The Escort on the other hand does not have a drain plug and takes almost 4 liters of oil so changing it is a royal pita, i put a new clutch in it in 2020 and drained and flushed it as the stuff that came out looked pretty ripe but no metal shavings that i could see.
 
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Ravenol MTF-2 75W-80 performed very nicely in my Mini's Getrag transmission.
Perfect shiftability and (as expected) crystal clear after two years and 20.000 km.
The only reason I'm back to BMW MTF LT-4 is it's 75W-90 and that's the factory fill.
I've been willing to take that risk for some time but going significantly thinner is still
a risk. The mentioned Castrol 75W-85 GL-4 apprears to be the ideal compromise if
there wasn't that availability issue.
You may also consider trying Castrol Transmax V 75W-80 instead of the Ravenol, again
GL-4. I did run Castrol Syntrans V-FE 75W-80 = Castrol Transmax V 75W-80 in my GTI
and it also felt great, almost same as VW G 052 527 (but not exactly same, very hard to
even describe the marginal difference). Currently I'm 'back' to 2.0 l G 052 527 + 0.5 l
Castrol Transmax V just because I had the OE stuff sitting around here for four years.
That said BMW MTF LT-4 75W-90 doesn't even nearly feel as good as Ravenol MTF-2
75W-80 in particular when cold. However that's what I did expect since MTF LT-4 is
roughly twice as thick compared to Ravenol MTF-2 both at 40°C and 100°C.
I often wonder why some people claim to not notice any differences when going that
much thicker. My personal conclusion to draw is some people aren't sentient enough
to assess differences in shiftability.
.
 
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