I left out an important word after micro.Parts are micro polished to reduce friction.The tolerences are closer with the types and quality of lubercations(synthetics) and cleaner blends also also reduce friction.Mirror like cylinder wall finishes and ring styles and materials have greatly improved engine life.Many of the import and commercial engines are warrantied for 100Ks miles some thing unheard of in years past.Actually we have some 600 hp Cummins diesals in our tracter trialer fleet(lowboy heavey haulers)that came with 500,000 mile warranty.engine building techonology has change,when I first started playing with cars 30/40K miles you were ready for rings,bearings, and valve job.We have many pieces of heavy equipment(dozer,excavators,etc)with over 10,000 hrs on them.One excavator(Kebelco)has 18,000 hrs with only in frame overhaul.Needless to say we have a good maintaince program.