You need to replace the cutting string periodically, but most models make this easy with a plug-in refillable string spool. If you have a gas-powered weed eater, you also need to replace the oil to keep the motor operating well, and refill it with gas to provide power. Seasonal maintenance, such as a thorough cleaning and proper storage, is important to keep your weed eater working properly. If you tackle a particularly dirty job, make sure to clean off any brush and debris before putting your weed eater away.