Breaking In a Rebuilt Engine

Read on to find out how IPD recommend this process be completed

Oil consumption problems can occur if an engine is not broken in correctly, allowing piston rings to seat properly. Rings are designed to apply a certain amount of tangential force outward, and compression rings rely on higher combustion pressures to force them down against the bottom of the piston's ring lands and outward to the cylinder walls.  Without this combustion force, these rings will not seat properly.  Note that oil control rings regulate the amount of oil film left on the cylinder wall to lubricate the compression rings, and each compression ring removes some amount of this oil film for proper oil control.

Although piston rings can seat without using a dynamometer, it remains crucial that an adequate load be placed on the engine to create enough combustion pressure and temperature to seat the rings (most critical within the first few hours of the engine's new service life).  Idling, increasing the RPM and hauling light loads will not create enough combustion pressure to seat new rings, only under load can engines obtain the pressure and temperatures required.

Our research indicates that minimizing idle time and operating a newly rebuilt engine at 75% of full load for at least the first 3 to 4 hours, produces satisfactory results in getting piston rings to seat.  The percentage of load and duration is variable between rebuilders as many already have a proven break in process; however, all agree that after initial start-up and checks are complete, that placing a load on the engine is vital to seating the rings.  Delaying this loading process can result in increased oil consumption.

Notice:  Approved Lubricants

The brand, type, classification & grade of oil used during the engine break-in period can affect the piston rings performance.

Use of an OEM recommended oil is preferred.  Additives & break-in oils should only be used according to the manufacturer's recommendations.