Technical Gear box oil

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Technical Gear box oil


New member
Feb 6, 2007
I'm planning on changing the gear box oil on my previously very neglected B. I read in the hand book one sort of oil, but then in the service cd it recommends ep80. I've bought some castrol ep 80 but have some valvoline 75w90 semi synthetic gear oil-would that be best? Which should i use for the best gear change/longevity of the gear box-any ideas more than welcome-the gl4 spec is met by the valvoline stuff by the way!
Mine is filled with automatic transmission fluid;)

Can you recommend a brand/SAE standard? Also, is there a property in the auto fluid that could cause issues in a manual box (for instance viscosity of the auto oil until it gets warm etc)........?

Like the idea of improving my sometimes stiff gearchange but don't want to do it at the cost of my gearbox seals or worse still my gearbox!! :eek:
Im not sure of the specific oil I have used, I need to check it out. I can say though that I have used it in several different cars with no seal problems etc
I'm pretty sure its every 70,000 miles according to the service book. There aren't really any indications of it needing to be changed, but all the swarf collects in the bottom of the box from normal wear and tear and also from gears being grinded and this needs to be drained out.
ep80 is a single grade oil, I would go for the synthetic 75w90 - something like Castrol Syntrax or the Valvoline mentioned above.

Auto transmission fluid is designed to do a different job, I wouldn't use it in a manual.
As I have no idea I'll just be referring to the service manual again, which says Tutela ZC 80S.