The Honda Fourtrax 350, also known as the Honda TRX350, has a recommended engine oil capacity of approximately 2.6 quarts or 2.5 liters. This measurement includes the oil required for both the engine and the oil filter. It's always advisable to consult the owner's manual for your specific model and year to confirm the exact oil capacity and other maintenance recommendations for your Honda Fourtrax 350. The manual will provide you with accurate and detailed information for your particular vehicle.