How do you know when to change the oil on your ZTrak™ Riding Lawn Mower? Why should you care? The fact is the engine oil in your ZTrak™Mower is critical to keeping it going. Not enough oil? You could ruin your engine. John Deere recommends you check your oil level before each use and change your oil once a season. That’s about every 50 hours of use. Changing the oil on your ZTrak™ Riding Mower is simple. Let’s go step-by-step and ensure you know how to do it right. For specific information and more details check your Operator’s Manual.