As of 2015, Polaris PS-4 and Polaris PS-4 Extreme Duty are the manufacturer’s recommendations for motor oils that work in a Polaris ATV. Both motor oils are full synthetic blends suitable for every season.
The Polaris PS-4 has a viscosity of 5W-50 and performs in a temperature range between -40 degrees Fahrenheit and 100 degrees Fahrenheit. The Polaris PS-4 Extreme Duty is a higher-viscosity 10W-50 grade, making it a professional-grade oil suitable for high temperatures and extreme duty. It performs in a temperature range between 0 degrees Fahrenheit and 130 degrees Fahrenheit. According to the owner’s manual, a 0W-40 API certified oil may work, though the oil may require changing more frequently.