MGB Gearbox Oil

MGB Gearbox Oil


Keep it stiff

Original Poster:

1,492 posts

133 months

Friday 24th July
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I was about to put fresh oil in my re-build box, I looked in the Haynes to check capacity and was surprised to see the recommendation of 20/50, I was expecting EP80/90.

I just Googled and I see this is a common question, from what I can see the consensus seems to be 20/50 in a box with OD but better to use EP in non-OD box. My box in non-OD, 4 synchro, early 60's and will be used for circuit racing. I would prefer to use EP, would you agree?


1,744 posts

191 months

Friday 24th July
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I was also confused when I first went to change my BGT's gearbox oil, having previously had a V8 as the V8 uses EP, which seems more correct for a gearbox. However the correct grade is 20/50. My MGA which is the same gearbox as an early B uses SAE 30,which is also recommended for the earlier B series engine. I think that 20/50 is acceptable as a later standard, not available when the MGA was introduced.


2,025 posts

168 months

Sunday 26th July
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Try and track something down similar to this. Most modern oils eat brass.


888 posts

129 months

Wednesday 21st October
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I'm back from the "Dark Side" TVR's. Just bought a 1974 GHN5 357680G roadster. Following the previous posts reference gearbox oils. What is the recommended oil for a gearbox with overdrive plus diff oil? Seems to be a well discussed subject? Any advice please? Cheers J C.