Gearbox oil

[Peter Cresswell]

Has any tried or considered using one of the modern 20w50 oils designed for the Mini in an MGB gearbox. It would appear to me that there may be some advantages in doing so, as they are a 20w50 engine oil but have additives to stop the oil shearing as the teeth mesh and also helps the synchromesh which relies on friction.
I know from my Mini Cooper days that Millers offer 2 versions. A full mineral oil called CLASSIC MINI OIL 20w50 (this might now be called Classic Trans M 20w50) at around £25 for 5l, and a semi synthetic oil CTV 20w50. CTV is expensive (around £50 for 5l) and probably overkill in a B Gearbox (but it does hold full oil pressure when nearly boiling!). These are the claims for the Classic version:

Description

Mineral based engine oil specifically developed to incorporate EP levels of gear protection for use in combined engine and gearbox applications. Also suitable for some classic motorcycles preferably non-roller bearing big end type where the clutch runs in engine oil.

Application

Use in installations where the engine and gearbox share the same oil such as original Mini, and gearbox applications specifying an engine oil. The best possible oil for discerning Mini owners.

User Benefits
◾Improved engine and gearbox protection versus a normal 20w50 engine oil.
◾Longer life for gears, plain bearings and needle/roller bearings
◾Improved gear change quality. Longer idler gear life in transverse Mini engines.

Any thoughts?

[George Wilder]

Peter
I have always used straight 20/50 engine oil in my 3 syncro box with O/D. Some 20+years since the rebuild and 60K+ miles - changing about 12K miles - with no ill effect.
Would this Mini 20/50 have any positives or negatives for the O/D I ponder?
George

[Peter Cresswell]

Hi George
I'm not suggesting that a straight 20w50 oil might give problems, just that there might be something better. Oils have moved on a lot in recent years! The O/D is a good point though and although it does use gears to transmit the drive, so in principle should be ok, the operating mechanism uses O ring seals, which might be a problem. I'll try contacting Millers to see what they think.

[Peter Cresswell]

I have recently received this response from Millers Oil regarding the use of the Mini Oils mentioned above in a gearbox with overdrive:
'Thank you for your enquiry and you will not have any problem in you using either of our two mini oils in your gearbox. These oils will not do any damage to the seals.'

I have now asked a supplementary question:
If there no problems, are there likely to be any advantages? I am awaiting a response to this one!

When I change the gearbox oil next, I am tempted to use the classic Mini oil which is a 20W50 mineral oil as it is about the same price for 5l as most other quality oils. I'm not sure about the CTV which is semi synthetic though, but it was no problem in my Mini Cooper's engine/gearbox, but for that application there was a clear advantage of it maintaining oil pressure when the oil it was extremely hot on climbs in the Alps. An MGB gearbox should be more kind to the oil.

[Adrian Oliver]

This is interesting.

I can't see any reason for not using modern oils in the engine and gearbox.

Unless anyone has other ideas?

[Dave Linkson]

I put Penrite classic 20/50 in my OD gearbox some months ago and all working fine