The 1999 Honda FourTrax 300 uses SAE 10W-40 motorcycle oil (API SG/SH or newer) and requires roughly two quarts when changing the oil and filter. Use an oil designed for four-stroke motorcycles with a wet clutch, not automotive oil.
In this report, we explain the specific oil type, capacity, and practical considerations for maintaining the TRX300’s engine and transmission. We cover how to select the right oil, how much to use, and a step-by-step guide to performing an oil change, as well as brand recommendations and climate considerations.
Oil type and capacity
The four-stroke TRX300 shares lubricant between the engine and transmission, so using a motorcycle oil that protects wet clutches is important. The recommended viscosity and API rating have historically been 10W-40, with API SJ/SL/SM or newer. There is no need for car-specific oil, and motorcycle oil is preferred for clutch compatibility.
Viscosity and clutch compatibility
Choosing the right viscosity helps start-up performance in cold weather and maintains film strength in hot weather. Oils labeled for four-stroke motorcycles with wet clutches (often API SM or higher and JASO MA/MA2) are appropriate.
Here are the main guidelines you should follow when selecting oil for the TRX300:
- Viscosity: SAE 10W-40 is standard for most riding conditions; 10W-30 or 5W-40 may be used in milder or hotter climates depending on manual guidance.
- Oil type: Motorcycle engine oil suitable for wet clutches; API SG/SH or newer; JASO MA/MA2 preferred.
- Clutch compatibility: Avoid oils with heavy friction modifiers that can affect the wet clutch’s performance.
- Capacity: Approximately 1.9 quarts (about 1.8 liters) when changing the oil and filter; check manual for exact figures for your bike.
Note: The exact capacity can vary slightly by model and whether the filter is replaced. Always verify with the owner's manual or service manual for your specific VIN and environment.
Brand options and climate considerations
Several reputable brands offer 10W-40 motorcycle oils that meet the TRX300’s requirements. Using OEM-sanctioned or widely compatible brands can simplify maintenance and ensure proper clutch operation.
Below are commonly recommended oil choices that meet the spec and are widely used by Honda ATV owners:
- Honda GN4 10W-40 API SG/SH or newer, designed for four-stroke motorcycles and ATVs.
- Motul 7100 10W-40 or Motul 4T 10W-40; synthetic options available that meet API SL/SN and JASO MA.
- Castrol Power 1 4T 10W-40 or Castrol GTX for older engines; check product specs for JASO MA/MA2 compatibility.
- Liqui Moly 4-T 10W-40 or similar motorcycle oils with appropriate approvals (API SN/SM, JASO MA/MA2).
When temperatures vary significantly, consider a slightly thinner or thicker oil within the same 10W-40 range to optimize cold-start or hot-performance. Consult your manual for climate-specific guidance.
Oil change procedure
Carrying out an oil change on the TRX300 is a straightforward maintenance task. Accurately draining, replacing the filter, and refilling will help preserve engine and transmission life.
- Warm up the engine briefly, then turn off and place the ATV on a stable stand or level surface.
- Remove the drain bolt on the engine sump and carefully drain the old oil into a suitable container.
- Remove the oil filter, clean the mounting area, and install a new filter with a light coat of oil on the seal.
- Reinstall the drain plug securely and tighten to the manufacturer’s torque specification.
- Fill with the recommended oil type and amount (roughly 1.9 quarts or about 1.8 liters is typical for an oil change with filter).
- Check the oil level with the dipstick or sight glass according to the manual, start the engine, and run briefly to circulate oil.
- Turn off, re-check level, add oil if needed, and dispose of old oil responsibly.
Following these steps helps ensure proper lubrication and hydraulic performance of the engine and transmission in the TRX300.
Maintenance tips and safety reminders
Always use fresh oil; avoid reusing old oil. Never mix synthetic and conventional oils without a plan, and follow the manual’s guidance on intervals and oil type. Wear eye protection and gloves when performing oil changes.
Summary
The 1999 Honda FourTrax 300 uses SAE 10W-40 motorcycle oil (API SG/SH or newer), with a typical change requiring about 1.9 quarts of oil including a filter. Use motorcycle oil suitable for wet clutches, and avoid automotive oils that contain friction modifiers. Brands such as Honda GN4 and other reputable motorcycle oils in 10W-40 are suitable. Always verify exact capacity and specifications in your owner's manual, as variations can occur by model and riding conditions.