Automatic Transmission Fluid Oxidation
Automatic transmission fluid will provide 100,000 miles of service
before oxidation occurs under normal operating temperatures of about
170°F. Above normal operating temperatures, the oxidation rate doubles
(useful life of fluid is cut in half) with each 20° increase in temperature.
The approximate life expectancy at various temperatures is as follows:
| 175°F | 100,000 miles |
| 195°F | 50,000 miles |
| 212°F | 25,000 miles |
| 235°F | 12,000 miles |
| 255°F | 6,250 miles |
| 275°F | 3,000 miles |
| 295°F | 1,500 miles |
| 315°F | 750 miles |
| 335°F | 325 miles |
| 355°F | 160 miles |
| 375°F | 80 miles |
| 390°F | 40 miles |
| 415°F | Less than 30 minutes |
This information clearly shows why transmission oil coolers and the
various maintenance intervals are recommended for severe usage.
Above 300°F, the metals inside the transmission will warp and distort
in varying degrees depending on the severity of overheat. Because this
damage occurs and fluid life is so seriously impaired, rocking out of
snow, mud or sand should never exceed a very few minutes.
