The tachometer shows engine speed in thousands of revolutions per minute (rpm).
CAUTION
Do not run the engine with the tachometer needle in the RED ZONE. This may cause severe engine damage.

NOTE
When the tachometer needle enters the STRIPED ZONE, this indicates to the driver that the gears should be shifted before entering the RED ZONE.
Speedometer, Odometer, Trip Meter and Trip Meter Selector (Without Multiinformation
Display)
Engine Coolant Temperature Gauge (Without Multi-information Display)Mazda 6 Owners Manual: Rocking the Vehicle
WARNING
Do not spin the wheels at more than 56 km/h (35 mph), and do not allow
anyone to stand behind a wheel when pushing the vehicle: When the vehicle
is stuck, spinning the wheels at high speed is dangerous. The spinning tire could
overheat and explode. This could cause serious injuries.
...
Mazda 6 Owners Manual: Dsc hu/cm inspection
1. Remove the battery and battery bracket.
2. Disconnect the DSC HU/CM connector.
3. Connect the SST (49 G066 004) to the DSC HU/CM connector and
harness side connector.
4. Inspect voltage referring the table below.
Terminal Voltage Table (reference value)
(Ignition switch is at ON, and conne ...