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: Setting the System
When the MODE switch is pressed, the Mazda Radar Cruise Control (MRCC) main indication
(white) turns on and the vehicle speed and the distance between vehicles while in
headway control can be set.
NOTE
When the ignition is switched to ACC or OFF while the Mazda Radar Cruise
Control (MR ...
Mazda 6 Owners Manual: Three-way catalytic converter (twc) inspection
Note
Make sure that no HO2S DTCs have been detected. If detected, this
inspection is not applicable for TWC inspection.
1. Connect the WDS or equivalent and monitor PIDs as following.
Monitor the right TWC using O2S11 PID for upstream HO2S and O2S12 PID
for downstream HO2S.
2. Be ...