How to Change the Oil on a Harley Fatboy

by Chris GillilandUpdated November 07, 2017

Items you will need

  • Socket wrench

  • SAE sockets

  • Oil filter wrench

  • 3 qts. 20W50 Engine oil

  • Oil catch basin or container

  • Towels or rags

  • Service manual (optional)

Changing the engine oil and filter is one of the basic maintenance skills every motorcyclist should have under their belt. When done on a regular basis, the lifetime of your Harley-Davidson Fat Boy will be extended by reducing wear caused by contaminated or degraded oil. Although the Fat Boy and most Harley-Davidson motorcycles use three types of oil, replacing the engine oil is a fairly simple task for most motorcyclists and requires only a few tools.

Start the motorcycle and let it warm up for a few minutes. Warm oil will flow better and will help flush out any contaminants that may be present in the oil. Be sure not to let the oil get too hot to prevent burning yourself in the following steps.

Locate the oil drain plug and place your oil catch basin below it. The plug is under the right side of the motor.

Remove the oil drain plug using a socket wrench and inspect the drain plug's O-ring for damage or tears, replacing the O-ring as necessary. Set the drain plug aside.

Remove the oil filter with an oil filter wrench and discard the old filter.

Allow the old oil to drain until the flow has reduced to a minimal trickle. Replace the oil drain plug.

Fill the new oil filter with fresh oil, coating the inner lip of filter lightly with oil to provide a stronger seal before screwing the filter onto the motor. Tighten the filter by hand until it is secure.

Add your engine oil into the oil tank from the oil fill neck (where the dip stick is mounted).

Replace the dip stick and wipe away any spilled oil.


If possible, consult a service manual for comprehensive details about this process and oil types and amounts.
Be sure that you have the right type of oil filter wrench for both the old and new filters. If you own a 2001 and newer Fat Boy, be sure that the replacement oil filter is capable of filtering down to 10 microns to accommodate the smaller oil passages used by the Twin-Cam 88 motor. Using a standard oil filter will prevent the flow of oil into the motor and will cause serious damage.
Remove the oil dip-stick to quicken the draining process. If you do not feel that you can complete this project, have the work done by a qualified technician.


Use caution when draining the oil to prevent burns. To prevent the oil from reaching extreme temperatures, only allow the motorcycle to warm up for a few minutes. Do not use tools or excessive force when tightening the oil filter to prevent damage. Double check that the oil filter cap or dip stick is secured before starting the motor again to prevent spraying oil. Do not dispose of used oil in a drain or trash can. Take it to an auto parts store for recycling.

More Articles

article divider