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The Honda Foreman Rubicon (TRX500) shares its oil between the engine and transmission, so the right weight matters more than on a typical car. Honda’s own GN4 oil is the factory-spec choice, but several 4-stroke ATV/motorcycle oils meeting JASO MA specs work just as well. Always confirm the correct weight for your model year (10W-30 on 2009+, 10W-40 on most earlier models) against your owner’s manual before buying.
| # | Product | Price | Where to buy |
|---|---|---|---|
| 1 | Honda GN4 10W-30 4-Stroke Oil | $10-$15/quart | Amazon · eBay |
| 2 | Honda GN4 10W-40 4-Stroke Oil | $10-$15/quart | Amazon · eBay |
| 3 | Maxima ATV Formula+ 10W-40 | $10-$14/quart | Amazon |
| 4 | Castrol Actevo 10W-40 4T | $8-$12/quart | Amazon · eBay |
| 5 | Yamalube All Purpose 4-Stroke Oil 10W-40 | $8-$12/quart | Amazon · eBay |
| 6 | Mobil 1 Racing 4T 10W-40 | $12-$16/quart | Amazon · eBay |
The picks, in detail
Honda GN4 10W-30 4-Stroke Oil
Honda’s factory-spec oil for 2009-and-newer Rubicon models, formulated for shared engine/transmission/wet-clutch use.
- JASO MA rated for wet clutches
- 10W-30 weight
- OEM-specified for late-model Rubicons
- Exact factory match for newer models
- Purpose-built for combined engine/trans systems
- Pricier than generic automotive oil
- Wrong weight for pre-2009 models
Honda GN4 10W-40 4-Stroke Oil
The correct Honda-branded weight for 2004-2009 Rubicon models, same JASO MA wet-clutch formulation.
- JASO MA rated
- 10W-40 weight
- OEM-specified for mid-2000s Rubicons
- Factory match for the most common Rubicon years
- Consistent OEM quality
- Not the right weight for 2009+ models
- Only sold through Honda dealers/parts sites
Maxima ATV Formula+ 10W-40
A popular aftermarket ATV-specific oil designed for shared engine/transmission/clutch systems like the Rubicon’s.
- JASO MA2 rated
- 10W-40 weight
- Formulated specifically for ATV powertrains
- Widely used and trusted in the ATV community
- Good wet-clutch friction performance
- Costs more than generic motor oil
- Still need to confirm weight matches your model year
Castrol Actevo 10W-40 4T
A widely available JASO MA-rated 4-stroke oil sold at most auto parts stores, a solid budget-friendly alternative to Honda GN4.
- JASO MA rated
- 10W-40 weight
- Semi-synthetic formulation
- Easy to find locally
- Lower price than OEM Honda oil
- Marketed primarily for motorcycles, not ATV-specific
- Slightly less ATV-community track record than Maxima
Yamalube All Purpose 4-Stroke Oil 10W-40
A cross-brand 4-stroke oil commonly used by ATV owners across Honda, Yamaha, and other makes.
- JASO MA rated
- 10W-40 weight
- Suitable for shared engine/transmission systems
- Good value for JASO MA-rated oil
- Common choice among multi-brand ATV owners
- Branded for Yamaha despite cross-compatibility
- Availability varies by retailer
Mobil 1 Racing 4T 10W-40
A full-synthetic 4-stroke option for owners who want extended oil-change intervals and stronger high-temp protection.
- JASO MA2 rated
- Full synthetic
- 10W-40 weight
- Full synthetic protection at higher temps
- Trusted mainstream brand
- More expensive than semi-synthetic options
- Overkill for light/occasional ATV use
Buying tips
- Confirm your exact model year before buying — Rubicons switched from 10W-40 to 10W-30 as the factory spec around 2009.
- Always use a JASO MA or MA2-rated oil since the Rubicon’s engine and wet clutch share the same oil.
- Change oil every 50 hours of use or once per season, whichever comes first, per Honda’s maintenance schedule.
As an Amazon Associate and eBay Partner, toptenpick.com earns from qualifying purchases. Prices and availability are subject to change.