Changing the oil in your Mazda 6 is one of the most important maintenance procedures you can perform on your car. The engine oil will break down over time from the heat in the engine and will lose it's effectiveness. Along with thermal breakdown, engine oil can pick up particles of metal from normal engine wear, and while these particles are supposed to be filtered out by the oil filter, some may get through. Changing the oil will remove those with the old oil. If neglected, old oil can damage the internal components of the engine.
Raise the front of your Mazda with a jack and support the front end with a set of jack stands. Raise the hood and remove the oil fill cover from the engine. Set it somewhere safe.
Position an oil drain pan under the oil drain plug and remove the plug with a socket and ratchet. Allow the used engine oil to drain into the pan. Replace the drain plug and tighten it with a socket and ratchet.
Position the oil drain pan under the oil filter and remove the filter with an oil filter wrench, turning it counterclockwise. Verify that the gasket came off with the filter and set the filter in the pan with the open side down to allow it to drain.
Fill the new oil filter with new oil. Lubricate the gasket on the filter with a small amount of fresh oil and install it on the car. Tighten the filter by turning it clockwise until it is tight. Do not use a wrench on the filter; hand tight is all that is required.
Support the car with the jack and remove the jack stands. Carefully lower the car back to the ground.
Move up to the engine compartment and pull the dipstick from the dipstick tube. Wipe the oil off it with a clean rag and set it aside for now. Fill the engine with new oil following the vehicle manufacturer's recommendation on type and quantity of oil needed.
Insert the dipstick into the dipstick tube, making sure it is fully seated in the tube. Remove the dipstick and check the level, making sure the engine oil is full. Reinstall the dipstick in the tube and push it down until it is fully seated in the tube.
Dispose of the old oil and filter properly. Most auto parts stores will accept the oil and filter for recycling and many of them will take it for free.