Vehicles with catalytic converters or oxygen sensors must use ONLY UNLEADED FUEL, which will reduce exhaust emissions and keep spark plug fouling to a minimum.
This vehicle will perform best with fuel listed in the table.

* U.S. federal law requires that octane ratings be posted on gasoline station pumps.
Fuel with a rating lower than 87 octane (91 RON) will negatively affect the emission control system performance and could also cause engine knocking and serious engine damage.
CAUTION
Leaded fuel is harmful to the catalytic converter and oxygen sensors and will lead to deterioration of the emission control system and or failures.
Gasoline blended with oxygenates such as alcohol or ether compounds are generally referred to as oxygenated fuels. The common gasoline blend that can be used with your vehicle is ethanol blended at no more than 10 %. Gasoline containing alcohol, such as ethanol or methanol, may be marketed under the name "Gasohol".
Vehicle damage and drivability problems resulting from the use of the following may not be covered by the warranty.
Emission Control SystemMazda 6 Owners Manual: Cell Phones
WARNING
Please comply with the legal regulations concerning the use of communication
equipment in vehicles in your country: Use of any electrical devices such
as cell phones, computers, portable radios, vehicle navigation or other devices
by the driver while the vehicle is moving is dangerous ...
Mazda 6 Owners Manual: Oil cooler flushing
Note
The contaminated cooler line (oil pipes and hoses) and auxiliary
cooler must be flushed completely when ATX is overhauled or replaced.
1. Remove the two oil cooler line hoses and apply air pressure of 196 kPa
{2.0 kgf/cm2, 28 psi} from the return hose (pipe) side.
Caution
Power ...