In article ,
Doctor Drivel wrote:
Not if quality "pure" synthetic oil is used", which is now rare as many
"fully synthetic" oils have petroleum base. "pure" synthetics can go to
well over 25,000 miles. Some have ran as long as 100,000 miles before
breaking down.

Oil gets contaminated in an engine. So it's not just the oil itself but
how well it is filtered etc and whether those contaminants can be removed
or not which determines its service life in practice. That's one reason
why lifetime oils for gearboxes etc have been around for a long time - but
not for engines.

As usual you have just visited a few websites and are quoting the bits
that suit you without any understanding of the subject.

--
*Few women admit their age; fewer men act it.

Dave Plowman London SW
To e-mail, change noise into sound.