A low level of electrolyte fluid will cause the battery to discharge quickly.

Inspect the electrolyte level at least once a week. If it is low, remove the caps and add enough distilled water to bring the level between the upper and lower level (illustration).
Do not overfill.
Examine the specific gravity of the electrolyte with a hydrometer, especially during cold weather. If it is low, recharge the battery.
Battery Maintenance
Battery RechargingMazda 6 Owners Manual: Oil cooler disassembly/assembly
1. Disassemble in the order indicated in the table.
2. Assemble in the reverse order of disassembly.
Radiator Outer Tank (In Tank Oil Cooler) Removal Note
1. Inspect the height of the header tabs.
2. Insert the end of a medium tip screwdriver between the end of the header
tab and the out ...
Mazda 6 Owners Manual: Oil pressure switch inspection
1. Verify that the oil pressure warning light illuminates when the ignition
switch is at ON position.
2. Verify that the oil pressure warning light goes off when the engine is
started.
If the oil pressure warning light does not illuminate or remains
illuminated, inspect the related wirin ...