hi sages- thanks for your answers. think nh has the most specific answer. makes sense that the volvo engine is likened to a tractor engine for reliability and durability. have only experienced 2 engines which have extreme longevity- the volvo 240 engine and the chrysler slantsix. did not know tractor engines in general were known for longevity. worked on two a ford and a john deere. while later models noticed both were quite simple and didnt have a lot of the power robbing devices/emisions equipment in cars which could shorten the life of an engine. farmers also are more mechanically inclined and would insist on a proven easy to work on reliable engine so their thin profit wouldnt frequently be soaked by a shyster dealer. also tractors tend to have very low gearing which would lighten the load on an engine and enhance its life. only surprise or bad design i have noticed on the volvo engine is its frequency of blowing head gaskets. seems with all the refinements in this engine the engineers would have figured out how to lick the weak head gasket design. thanks oldduke q