Boîte automatique à convertisseur (AT), CVT et double embrayage (DCT/DSG) : fluides et longévité
Différences techniques entre boîtes planétaires, CVT à courroie métallique et boîtes à double embrayage humide/sec, avec intervalles de vidange.
| Planetary Automatic (6AT–10AT) | Low-viscosity ATF (Dexron VI / Mercon ULV / ZF Lifeguard) · 60,000 km |
|---|---|
| Steel-Belt / Chain CVT | Dedicated high-traction CVT fluid (NS-3 / CVTF FE) · 45,000–60,000 km |
| Wet-Clutch DCT / DSG | DCTF + external cartridge filter · Every 60,000 km (37,500 mi) |
| Operating ATF Temp Window | 75–95 °C normal · >115 °C accelerates oxidation exponentially |
1. Why ATF and CVTF Are Chemically Incompatible
Conventional Automatic Transmission Fluid (ATF) contains friction modifiers designed for smooth clutch pack engagement in planetary gearsets. Continuously Variable Transmission Fluid (CVTF) requires a high metal-to-metal traction coefficient so the steel push-belt or chain does not slip against the variable-diameter variator cones. Pouring standard ATF into a CVT causes catastrophic variator scoring.
2. Transmission Coolers and Heat Exchangers
Many compact crossovers route transmission fluid through a compact water-to-oil heat exchanger mounted on the gearbox housing. Cleaning radiator fins and replacing engine coolant on schedule prevents transmission fluid overheating during summer mountain climbs or trailer towing.