A lawn more engine break-in could more accurately be described as an engine wear-in period. There are many variations and opinions of exactly what the best procedure to follow when breaking in or wearing in a new engine. The purpose, however, is to allow the piston rings and associated bearings to properly seat, resulting in an extended service life and improved performance of the engine. Another key step with engine break-in is to drain the warm oil after first use to flush out leftover or newly generated metal wear debris.
Check the factory-filled oil level in the lawn mower engine to ensure it is at the fill line. Pull out the oil dip stick, wipe it clean and replace it. Remove the dip stick again to check for the proper fill and ensure a more accurate reading.
Start the lawn mower. Allow it to run at normal idle speed for two to three minutes as the engine warms up during break-in period and for normal use.
Gradually bring the lawn mower engine up to normal speed over the course of just a few seconds. Engage the mower blades and mow a section of the yard for 20 to 30 minutes. Disengage the mower blades and slowly bring the engine to idle speed when this is completed.
Operate the engine at idle speed for two to three minutes and kill the engine. Drain the oil from the engine while it is still warm and to allow for more wear or foreign debris inside the engine to drain out.
Refill the engine with 30 weight detergent oil to the fill line of dip stick and use the lawn mower normally for the rest of the season. Change the oil and all filters at the end of the season.