There are differences in the synthetics which are used for turbine,
gearbox, recip. engines (2-stroke or 4-stroke) and other mechanical
devices.
There are differnces in conventional lubricants as well.
The proper weight of lubricants should be used in the proper
application.
One advantage of a synthetic is water does not readily mix with it as
it does with conventional oils and is also more heat tollorant.
Are you aware there is no cleanliness standard for oil?
Ever look at the bottom of an empty oil bottle? Sometimes there is
sediment.
This is why many industrial plants are using filter carts as part of
their preventive maintenance (PM) program.