Auto-RX and sludge
This oil sludge seems to have become a problem for many autos, NOT just Toyota.
Nor is the reason why accurately known. Some say the oil change intervals are too long; many owners do not care and trade every three -five years..
Too many short runs
Emission controls(high operating temps for better combustion)
This fairly new product "Auto-RX" claims to alleviate this condition.
I am skeptical of any mechanic in a bottle.