Originally Posted by 
Bush65
				
			 
			Back in the older days, especially with cast iron cylinder bore and rings the quickest way to run in was to drive so there were alternating small period of coasting followed by high load.
 
What then happened was while coasting low cylinder pressure helped to draw lubrication up around the rings, in preparation for the high pressure behind the rings during the high load.
 
Now with hard chrome plated rings, they take a very long time to bed in - so the above procedure doesn't work as well.
 
Further to this the Isuzu liners have a hard chrome plating that has some porosity to hold lubricant.
 
The improved precision plus hard chrome plating of wearing surfaces means bedding in is not normally required, but high loads for extended periods should be avoided between coasting periods (for upper cylinder lubrication - as above).