How to Change the Oil in a Push Lawnmower (Example: Craftsman, Murray, Briggs & Stratton Engines)

July 28, 2008 | by Fred (email) |

Regular lawnmower maintenance is essential to ensure your lawnmower stays in top running condition. You should perform complete maintenance on your mower at least once per cutting season to maximize the mower’s life, and to ensure your grass is cut perfectly every time.

This article is one in a series of maintenance articles that provide complete coverage of lawnmower care.   While not the most glamorous of topics, its a job many of us put off far too long.  Want to learn more about mower maintenance?  We’ll also teach you how to:

• sharpen a lawnmower blade using a grinder,
• replace a mower’s air filter; and,
• check and/or replace a lawnmower spark plug.

We’ll be performing maintenance on two mowers: a Murray with a 4.5 horsepower (HP) Briggs and Stratton engine, and a Craftsman self-propelled push mower with a 6.5 HP B&S engine.

Note that this tutorial is for general information only and isn’t a replacement for the maintenance instructions included in the mower. You should always follow those instructions to maintain your mower properly.

Finally, lawnmowers aren’t the only thing in your garage or shed that should be maintained this way. Any gas powered yard equipment, like pressure washers, chipper shredders, and string trimmers require regular maintenance to keep them running smooth. Most of the principals in this series will apply to all of these types of equipment.

Changing the Oil in a Push Lawnmower

Changing the oil in any gas powered 4-cycle engine ensures the engine stays well lubricated. This keeps the cylinder and piston moving freely against once another, and ensures that scarring doesn’t occur on either, increasing the life of the engine. Changing the oil also offers more immediate benefits: it reduces overall gas consumption, and allows the engine to burn more efficiently, which is better for the environment.

Step 1: Determine whether the engine has an oil drain plug, or if the oil must be drained by turning the mower over. Most push mowers have no drain plug and will need to be turned over to empty the oil.

Step 2:If the mower has a drain plug, unscrew the plug and let the oil drain into a funnel down into a pan.  If the mower has no drain plug, unscrew the oil cap, and tip the mower away from the side that the air filter is on.  This reduces the chances of the air filter being drenched in oil, which can occur on some engines.

Allow the oil to drain for 45-60 seconds, or until very little is flowing out of the mower.  A typical oil change will drain about 3/4 of the oil in the mower.  The remaining 1/4 will remain inside the engine, clinging to internal parts.

Step 3: Identify the right oil for your engine.  In some cases, the engine will have the oil type listed on a tag on the engine.  The maintenance manual will always include the right type of oil to use.  Many 4-cycle, small Briggs and Stratton engines take SAE 30 4-cycle Small Engine Oil available at home improvement and auto supplies stores everywhere.

Step 4: FIll the oil resevoir with oil.  Be sure to fill only until the dipstick registers “full.”  If you overfill, the lawnmower will billow white smoke as the excess oil is burned off during combustion.  An engine that is slightly overfilled will exhibit this behavior going up and down hills.  Note in the picture below that the top of the Craftsman dipstick indicates a 20oz. capacity; however, this is an “empty” capacity, not a “change capacity.”  In this case, we started by adding 10oz., then checking the dipstick every 2-3 oz. until it registered full.

Step 5: Perform the remainder of your maintenance, or start the mower if you are done with maintenance.  The mower should be running smooth (or at least smoother than it was running).  If the mower isn’t running smooth, check these steps and ensure you’ve done everything correctly.  Changing the oil a second time likely won’t solve the problem unless you’ve made a mistake.  You’ll notice if you check the oil again that it has turned brown.  This is because the new oil and old oil have mixed together.  This is OK and is not indicative of a bad change.

What do you think? How often do you change your lawnmower’s oil?  Are you due for a change and putting it off?