One question, was a proper break-in done on the engine that your aware of?
Also an addition from the service manual.
For a new engine, change oil after the first 20 hours of
operation. Thereafter, change oil after every 100 hours
of operation.
For an overhauled engine, use 10W-30 weight service
class SG, SH, SJ or higher oil for the first 5 hours of
operation. Change the oil after this initial
run-in period. Refill with service class SG, SH, SJ or
higher oil as specified in the Viscosity Grades table
on page 6.1.
Also an addition from the service manual.
For a new engine, change oil after the first 20 hours of
operation. Thereafter, change oil after every 100 hours
of operation.
For an overhauled engine, use 10W-30 weight service
class SG, SH, SJ or higher oil for the first 5 hours of
operation. Change the oil after this initial
run-in period. Refill with service class SG, SH, SJ or
higher oil as specified in the Viscosity Grades table
on page 6.1.