Why Your Gearbox Fluid Needs Changing — No Matter What the Manual Says

A sponsored feature from Motul South Africa's head of sales and technical takes aim at the widespread belief that transmission fluid never needs replacing. While South African motorists are disciplined about engine oil changes, gearbox fluid is typically ignored until something fails — and the piece argues that "filled-for-life" in an owner's manual really just means the fluid will last until the transmission gives out.

The article explains that all modern transmission types — torque-converter automatics, dual-clutch units and CVTs — suffer from heat, with operating temperatures regularly exceeding 100°C. That degradation forms varnish and sludge, thins the oil film protecting moving parts, and circulates abrasive wear metals. Stop-start traffic, towing and sustained highway cruising count as "severe use," and where manufacturers do specify intervals, they generally call for dual-clutch or CVT fluid every 40,000–60,000 km and around 80,000 km for conventional automatics.

Even then, a standard gravity drain only removes roughly 60% of the fluid, leaving degraded oil trapped in the torque converter, cooler and internal lines to contaminate the fresh fill. The piece promotes Motul's Evo flushing machine, which hooks up to the transmission's cooling lines and claims to swap out 99% of the old fluid across the whole circuit, dissolving deposits without any disassembly. A Johannesburg partner workshop, ASAP Motors, describes gearboxes arriving with pitch-black, metal-laden fluid and reports dramatic improvements in shifting after adopting the system.

Framed against an economy where stretching the life of the car you already own beats taking on new debt, the article positions regular gearbox servicing as one of the highest-return maintenance investments a motorist can make.