In the past, the engine break-in period was very important to the overall life and durability or the engine. The break-in period required has changed over the years with improved piston ring materials and designs. The break-in period now is short in comparison with that of engines of the past. Aluminum cylinder bore engine piston rings break-in faster than those used on case iron cylinder bores.

In general, there is no special engine operation procedure required during the break-in period. Break-in period is accomplished at any speed above idle and may occur faster if the engine is operated at varying loads and speeds. However, break-in occurs at an acceptable rate if the engine is operated at slightly less than top no-load speed with or without a moderate load. Combustion pressures at this speed are sufficiently high to cause piston rings to conform to the cylinder wall. It is recommended that an engine not be operated continuously at full load during the initial hours of operation. This can lead to permanent deformation of the cylinder bore.

It is very important to perform the initial break-in oil change, however. After the first 5 - 10 hours of operation, the oil should be changed to remove asperities that have broken from the bearings of the engine components and cylinder wall. Break-in can be performed using the recommended grades of standard or synthetic oil.