1. Park the vehicle on level ground.
2. Remove the oil level plug and washer.
3. Verify that the oil is near the brim of the plug port.
Specified oil grade API Service GL-4 or GL-5
Specified oil viscosity All-season: SAE 75W-90
Above 10 ° C {50 ° F}: SAE 80W-90

4. Install a new washer and the oil level plug.
Tightening torque 40-58 N·m {4.0-6.0 kgf·m, 29-43 ft·lbf}
Manual transaxle
Transaxle oil replacementMazda 6 Service Manual: Disconnection of the negative battery cable
Before beginning any work, turn the ignition switch to LOCK position,
then disconnect the negative battery cable and wait for more than 1 minute
to allow the backup power supply of the SAS unit to deplete its stored
power. Disconnecting the battery cable will delete the memories of the
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Mazda 6 Service Manual: Generator removal/installation
Warning
When the battery cables are connected, touching the vehicle body with
generator terminal B will generate sparks. This can cause personal injury, fire,
and damage to the electrical components. Always disconnect the battery negative
cables before performing the following operation.
...