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: Installation of radio system
If a radio system is installed improperly or if a high-powered type is used,
the CIS and other systems may be affected. When the vehicle is to be equipped
with a radio, observe the following precautions:
Install the antenna at the farthest point from control modules.
Install the antenna fe ...
Mazda 6 Owners Manual: Accessory Sockets
Only use genuine Mazda accessories or the equivalent requiring no greater than
120 W (DC 12 V, 10 A).
Front
The ignition must be switched to ACC or ON.
Center
The accessory sockets can be used regardless of whether the ignition is on or
off.
CAUTION
To prevent accessory socket damag ...