You’re advised to change your gearbox oil filter at the same time as when you do your oil.
If you have a gearbox leak repaired, then always change your oil after the repair to make sure it’s fully topped up.
Because the variety is so wide, a good way to gauge the health of your oil is to check its colour.
New oils are brightly coloured – usually red – and semi-transparent, but they turn into a darker shade, lose transparency and can smell burnt due to oxidisation as they degrade or build up deposits.
Source: | This article originally belongs to Express.co.uk