Using this oil change kit for your 2015 - 2021 Subaru WRX is easy. First, make sure your engine is cool. Then, locate the oil drain plug under your car and place a drain pan beneath it. Remove the drain plug and let the old oil drain completely. Replace the old drain plug gasket with the new one from the kit and put the drain plug back on. Next, find the oil filter and use an oil filter wrench to remove it. Put the new Subaru high - capacity oil filter on, applying a bit of new oil to the gasket first. Finally, pour in the Motul synthetic engine oils included in the kit. Check your owner's manual for the correct oil level. Note that Subaru recommends 5W30 from the factory, but 5W40 can be a good choice in hot climates. For maintenance, change your oil regularly according to your car's usage and the manufacturer's guidelines. Keep an eye on your oil level between changes and if you notice any leaks, check the drain plug and oil filter.