Running In of New or Rebuilt Engines

The purpose of running-in diesel engines is to reduce the severity of the surface roughness of critical mating surfaces (journals / bearings, rings / liners, etc.) thus increasing the contact area.  Defects on these surfaces, in new or re-built diesel engines, have the effect of reducing the actual contact areas (values of 1/1000 of the specified design area have been measured). Improvement is achieved by controlling the initial wear that takes place. The benefits include reduced long-term wear and energy losses due to friction.

Running-in occurs in two stages:

Stage 1: Removal of surface roughness

Stage 2:Correction of surface imperfections (poor machining tolerances and distortion)

After assembly most diesel engines are initially run up to full load for periods which may last as long as 2.5 hours on test beds. Most of the time, despite this severe running period Stage 1 is very often incomplete.  It therefore follows that Stage 2 will not have been reached by the time the unit has been put into service. Unless this is properly controlled, engine failures can result if the loading is increased too fast or too slow.

Symptoms of failure include:

• Lack of power 

• High oil consumption

• Oil exiting from the exhaust (breathing)

• Cylinder bore gazing

These are usually evident before 5000 miles or approximately 200 hours have been completed.

It is well documented that if new or re-built diesel engines are operated under conditions of low load / constant speed, running-in can be prevented and bore glazing is the most likely outcome.  This mode of operation is usually associated with commercial vehicles, agricultural / plant equipment and generators.

Cylinder bore glazing is caused by a combination of iron oxides, graphite and lubricant additives that form a hard chemical layer that prevents the running-in process from taking place. The process occurs before the piston rings generate load carrying surface plateaux or optimum oil control capability.

Bore glazing afflicts normally aspirated diesel engines more than turbo-charged versions that generate higher load factors and piston ring pressures.

Most piston rings are chrome plated and the best lubricant choice for running-in would be a straight mineral oil. However, combustion by-products coupled with high running temperatures have to be effectively dealt with and require detergency and dispersancy additives to provide engine protection.

Morris Golden Film  Running In Oil has been formulated to allow the desirable amount of wear whilst providing the correct balance of detergent and dispersant for engine component cleanliness.  It is recommended that Morris  Golden Film  Running In Oil is used for a minimum of 500 miles or 25 hours before the appropriate service fill lubricant is used.