How to Change the Oil in a 2021 GAS GAS EX 300

Shop parts for a 2021 GAS GAS EX 300 Dirt Bike.

Keeping your 2021 GAS GAS EX 300 in peak form means staying on top of routine maintenance—changing the transmission oil is one of the most critical. Changing the oil not only extends your bike’s life but ensures consistent, reliable performance out on the trail or track. This step-by-step guide, proprietary to MotoSport.com, gives you everything you need to change the oil yourself—saving time, money, and potential performance headaches down the road.

Tools and Supplies Needed

  • Allen wrench or socket set (6mm is common for drain and fill bolts)
  • Oil drain pan
  • Measuring jug with milliliter/cc markings
  • Fresh transmission oil (see owner's manual, commonly 10W-40 for this model)
  • Clean rags or shop towels
  • Engine Oil Drain Tool Long ODT Kit (recommended for a cleaner job)
  • Torque wrench (optional, for proper tightening)
  • Replacement crush washer for the drain bolt (recommended)
  • Funnel (to avoid spills)
  • Nitrile gloves (to keep hands clean)

Model-Specific Notes for the 2021 GAS GAS EX 300

  • This model does not use an oil filter on the transmission side; just change the oil regularly .
  • Oil capacity is 900 ml (0.9L). Do not overfill—overfilling can affect clutch performance .
  • Factory and aftermarket skid plates typically have drain access holes; you do not need to remove the skid plate for this service .
  • A long ODT kit may be installed to help keep things clean and prevent making a mess during drainage .

Step-by-Step Oil Change Instructions

  1. Warm Up the Engine
    Start the bike and let it idle for about 2–3 minutes. This ensures the oil is warm, which helps it drain thoroughly.
  2. Prepare Your Work Area
    Place the bike on a center stand or secure it upright with a stand. Lay down shop towels to protect your garage floor.
  3. Locate the Drain Plug
    The drain plug is on the bottom of the engine, directly beneath the transmission case. You should find an access hole in the skid plate aligned with the plug .
  4. Remove the Drain Plug
    Position your oil drain pan under the plug. Use a 6mm Allen wrench/socket to remove the drain bolt. Allow the oil to drain completely. If using a Long ODT drain tool, attach it and direct the hose into your oil pan for a cleaner job .
  5. Inspect and Clean
    Examine the drain plug for any metal particles, which can indicate excess wear. There is typically a small screen at the bottom of the plug—wipe this screen clean .
  6. Replace the Crush Washer
    It’s good practice to replace the washer under the drain plug to help prevent leaks. Reinstall the plug by hand at first, then snug it up with your wrench (do not overtighten; refer to your owner's manual for torque specification if possible).
  7. Refill with Fresh Oil
    Remove the fill plug, located on the side of the engine. Using a funnel and measuring jug, carefully pour in 900 ml of fresh oil . To avoid spills, pour slowly and in increments if necessary.
  8. Check the Oil Level
    Some models have a sight glass or dipstick. Ensure oil is within the recommended range/markings. Wipe away any spillage around the fill port and reinstall the fill plug securely.
  9. Double-Check for Leaks
    Start the engine and let it idle for a minute. Shut it off and examine the drain plug and fill cap area for any signs of leakage. Wipe down excess oil if needed.
  10. Dispose of Used Oil Properly
    Pour used oil into a sealable container and take it to a recycling center or auto-parts store for proper disposal.

Pro Tips and Warnings

  • Do not overtighten the drain bolt—stripping the threads is a common mistake.
  • Always use oil specified in your owner’s manual for optimal clutch and gear performance.
  • Record your mileage or hours to keep your service schedule on track.
  • Overfilling can be as bad as underfilling—always measure carefully.
  • The process for 2021-2025 EX/EC/MC 125-300 models is nearly identical, but always confirm your model year and specs .

Conclusion

Changing the oil on your 2021 GAS GAS EX 300 is a straightforward routine that protects your investment and performance. With the right tools and attention to detail, most owners can tackle this service at home with confidence—and keep their bike ready for the next adventure. For proprietary parts, recommended tools, and OEM oil, trust MotoSport.com to keep your ride running strong.

Related Shopping Categories

Shop Motor Oil for a 2021 GAS GAS EX 300 Dirt Bike.

Shop Oil Filters for a 2021 GAS GAS EX 300 Dirt Bike.

Shop Oil Drain Pans for a 2021 GAS GAS EX 300 Dirt Bike.

Shop Tools for a 2021 GAS GAS EX 300 Dirt Bike.

Shop Oil Fillers and Drain Plugs for a 2021 GAS GAS EX 300 Dirt Bike.

Disclaimer: This guide is provided for general informational purposes only and is not intended to replace your motorcycle's official owner's manual. Always refer to your manufacturer's documentation for model-specific instructions, torque specifications, safety procedures, and maintenance requirements. If you are unsure or inexperienced, consider seeking assistance from a qualified mechanic or technician.