how long after does synthetic oil like royal purple
start sludging or breaking down i chang oil after
6000 kms but wanna go farther too like 10 000
so when does synthetic break down i no synthetic
oil claims too not sludge engine when the additive
package is fresh but what about after 6-10.000

kms does it start or will it start sludging if you
leave it in too long?

That's a very valid question. After using synthetics for decades now I still suggest on time oil change intervals which for most would be the 3 mo. / 3,000 mile 0r 3 mo. / 5,000 km suggestion.

IMO - the oil itself would last forever except in use it's picking up contaminants like fuel, moisture just from condensation and suspending debris that isn't all caught by an oil filter so at the end of the time period or distance it isn't really the pure product you began with anymore. The contaminants AND certain additives seem the be the source of sludge - exacerbated by extreme heat.

Ages ago it was said that if you never shut an engine off and it drove steadily at uniform temps the oil would last near forever but that just doesn't happen in real world conditions,

T
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Tom Greenleaf - MetroWest, Boston