Upshifting
For normal acceleration and cruising, Mazda recommends these shift points:

*1 Always observe local speed limit regulations.
Downshifting
When you must slow down in heavy traffic or on a steep upgrade, downshift before the engine starts to overwork. This gives better acceleration when you need more speed.
On a steep downgrade, downshifting helps maintain safe speed and prolongs brake life.
Shift Gear (Shifting) Speed Limit
Direct ModeMazda 6 Owners Manual: Discharge headlight service warnings
Discharge headlight bulb service warnings
To prevent electrical shock when replacing the discharge headlight bulb,
dry hands thoroughly, and carry out work in an area out of rain.
When the light switch is on, approx. 25,000 V of high voltage passes
through the discharge headlight bulb so ...
Mazda 6 Owners Manual: Solenoid valve removal/installation
1. Disconnect the negative battery cable.
2. Remove the under cover.
3. Remove the control valve body. (See CONTROL VALVE BODY REMOVAL.)
4. Remove the solenoid valve(s).
5. Apply ATF to a new O-ring and install it on the solenoid valve.
6. Install the solenoid valve in the control valve body. ...