The engine on most Honda Foreman four-stroke ATVs uses a 10W-40 four-stroke engine oil that meets API SN or newer, with Honda GN4 10W-40 commonly cited as a recommended option. The Foreman also requires a separate transmission/gear oil in the gear case, not engine oil. Always confirm the exact specifications for your model-year in the owner’s manual.
Honda Foreman models use two separate lubrication systems: one for the engine and one for the transmission gear case. The exact viscosity and spec can vary by year and climate, so checking the official manual or a dealer for your specific machine is the best practice. If you don’t have the manual handy, you can often download a PDF from Honda’s official site or contact your local dealer for the correct specs and service intervals.
Engine oil recommendations
Below are common guidelines used for Foreman engine oil. These options reflect typical recommendations, but your manual is the final authority, as some model years or climates may have variations.
- Viscosity: 10W-40 is widely recommended for a broad range of temperatures; 10W-30 may be suitable in hotter climates; 5W-40 is used only if the manual specifies it for extreme cold or particular models.
- Specification: API SN or newer (such as SM, SL, or SJ). Honda GN4 10W-40 is a frequently cited example, but any 4-stroke ATV/motorcycle oil meeting API SN or newer is acceptable.
- Oil type: Conventional or synthetic is acceptable if it meets the required spec; many riders choose synthetic 10W-40 for better high-temperature stability and easier cold starts in cold weather.
- Capacity and change interval: Refer to your manual for exact engine oil capacity and replacement interval; after filling, run the engine briefly and recheck the level to ensure proper fill.
In practice, many Foreman owners run 10W-40 API SN or newer engine oil and perform oil changes per the manual’s schedule (typically annually or after a set number of hours, depending on usage). Always verify the exact requirements for your year and riding conditions.
Gear oil and transmission lubrication
The Foreman’s transmission/gear case uses a separate lubricant, and engine oil should not be used in this compartment. The typical specification is a GL-4 gear oil in the 80W-90 range, though some manuals allow other GL-4 grades or viscosities depending on the model year and climate. Always consult the owner’s manual for the exact requirement.
- Gear oil type: GL-4 80W-90 is the most commonly cited baseline for many Foreman models; some years may list 75W-90, 85W-90, or similar GL-4 options. Do not use GL-5 unless your manual allows it.
- Do not mix oils: Use the gear oil specifically in the gear case; do not substitute engine oil in the transmission.
- Filling and level: Use the designated fill plug and bring the oil to the specified level per the manual; avoid overfilling.
- Change intervals: Gear oil change intervals vary by model and usage; check the manual for recommended timing (hours of operation or seasonal intervals).
Because exact grades and capacities differ by year and model, verify the precise gear oil specification for your Honda Foreman from the owner’s manual or your Honda dealer.
Summary
For a Honda Foreman, use a four-stroke engine oil such as 10W-40 that meets API SN or newer, with Honda GN4 10W-40 as a common reference point. The transmission/gear case requires a separate GL-4 gear oil (commonly around 80W-90), not engine oil. Always refer to your specific model-year manual for exact viscosity, grade, capacity, and service intervals, and avoid mixing engine oil and gear oil. Regular, model-accurate oil changes help ensure reliable performance and longevity of your Foreman.