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: Crash zone sensor removal/installation
Warning
Handling the crash zone sensor improperly can accidentally deploy the air bag
module and pre-tensioner seat belt, which may seriously injure you. Read AIR BAG
SYSTEM SERVICE WARNINGS before handling the crash zone sensor. (See SERVICE
WARNINGS.)
1. Turn the ignition switch to LO ...
Mazda 6 Owners Manual: Excessive Speed Warning
If the vehicle speed exceeds the speed limit sign displayed on the active driving
display, the warning sound is activated and the area around the speed limit sign
displayed on the active driving display flashes 3 times in amber, and if the vehicle
speed continues to exceed the displayed speed ...