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: No.8 no cool air
When performing an asterisked (*) troubleshooting inspection, shake the
wiring harness and connectors while performing the inspection to discover
whether poor contact points are the cause of any intermittent malfunctions.
If there is a problem, check to make sure connectors, terminals ...
Mazda 6 Service Manual: Thermostat
THERMOSTAT REMOVAL/INSTALLATION
1. Remove the plug hole plate.
2. Disconnect the negative battery cable.
3. Drain the engine coolant. (See COOLING SYSTEM SERVICE WARNINGS.)
4. Remove the drive belt. (See DRIVE BELT REPLACEMENT.)
5. Remove the washer tank.
6. Remove the P/S oil pump.
Note
...