The Foreman 400 uses 10W-40 motorcycle oil and requires about 2 quarts (roughly 1.9 liters) for a full oil change with a new filter. Automotive oil is not recommended for this ATV engine due to different lubrication and clutch requirements.
The 1998 FourTrax Foreman 400 is a 398cc four-stroke ATV engine. Oil grade, capacity, and service intervals are specified in Honda’s owner and service manuals. For reliable lubrication, rely on oils formulated for motorcycles rather than automotive engine oils, and adhere to Honda’s viscosity and API recommendations.
Oil specifications for the Foreman 400
Below are the typical oil guidelines that have historically applied to this model. Always verify with the official owner’s manual for your exact unit, as there can be variations by year or market.
- Recommended oil grade: 10W-40
- Suitable oil type: motorcycle engine oil that meets API SG/SH or newer standards
- Common OEM recommendation: Honda GN4 10W-40 or equivalent automotive-motorcycle oils labeled for four-stroke engines
- Engine oil capacity: approximately 2 quarts (about 1.9 liters) with the oil filter change
When selecting oil, prioritize motorcycle-specific formulations and API ratings rather than car motor oils, to ensure proper clutch performance and engine protection in the Foreman’s wet-clutch setup.
Recommended oil options
Here are commonly accepted choices that fit the Foreman 400’s specifications. The list highlights oils that are widely used and documented as compatible with this model.
- Genuine Honda GN4 10W-40 motorcycle oil (or equivalent API SG/SH/SN rating)
- Other 10W-40 motorcycle oils that meet API guidelines and are designed for four-stroke engines
- Synthetic or semi-synthetic motorcycle oils labeled for four-stroke engines, provided they meet the API rating
Always check the oil label to confirm viscosity and API certification. If you’re unsure, consult your Honda dealer or the service manual for the exact specification for your bike’s year and region.
How to change the oil on a 1998 Foreman 400
To perform a standard oil change, follow these general steps. A clean, level work area and proper disposal for used oil are essential.
- Warm the engine briefly, then park the ATV on a level surface and place a drain pan beneath the engine.
- Remove the oil drain plug and allow the old oil to drain completely. Replace the drain plug seal if needed.
- Remove the oil filter (if equipped) and install a new filter, ensuring the gasket is lubricated with a little fresh oil before installation.
- Install the drain plug securely, then fill the engine with the recommended amount of 10W-40 motorcycle oil. Use a little at a time and check the level frequently.
- Run the engine briefly to circulate the new oil, turn off, wait a few minutes, and check the oil level again. Add oil as needed to reach the correct level.
- Dispose of the used oil responsibly and record maintenance in the vehicle’s service log.
Following these steps helps ensure proper lubrication and avoids oil leaks or overfilling, which can affect engine performance and reliability.
Maintenance notes and reminders
Always refer to the specific owner’s manual or service bulletin for your exact VIN and market, as there can be regional differences in capacity or recommended oil type. Using a motorcycle-grade oil aligned with API specifications is key, and avoid car engine oils that can have unsuitable additives for a wet-clutch ATV engine.
Summary
In summary, a 1998 Honda Foreman 400 takes 10W-40 motorcycle oil, with an approximate change capacity of two quarts when replacing the filter. Use oils designed for four-stroke motorcycles that meet API SG/SH or newer standards, and consider Honda GN4 10W-40 as a reliable option. Always consult the owner’s or service manual for your specific model year and region to confirm exact capacity and specifications, and perform oil changes with proper disposal and care.