Allison C4

Allison C‑4 approval is a technical standard developed by Allison Transmission for automatic transmissions used in heavy trucks, buses and special equipment. Lubricant that meets this requirement must provide a stable viscosity in the range of 9.5‑12.5 cSt at 100 °C, high oxidation resistance, protection against wear and corrosion, and also optimal operation of the torque‑converter clutch. The specification is targeted at Allison 1000‑2000‑Series transmissions, including 3000‑Series models, installed in diesel engines of 250 kW and above. Since C‑4 does not contain restrictions regarding SAPS, it is compatible with after‑treatment cleaning systems (DPF) and catalysts, provided they do not require low sulfate content. Products approved under C‑4 are usually also compatible with the previous Allison C‑3 requirements, allowing safe lubricant upgrades without changing the transmission.