What is good to put in an enginge to stop oil leaks that will not harm the engine.
New seals. But if your engine is tired to the point of building up excess crankcase pressure you’re fighting a losing battle.
Any of the stop leak products at the auto parts store that is made for engine oil should work, unless the problem is due to elevated crank case pressure, as mentioned, or badly worn and damaged seals. ‘Gold Eagle’ brand is good, and any ‘high-mileage’ motor oils also contain the same additives to help soften old and dried-out seals.
what kind of oil leaks r u talking about? from the exhaust? the block? the valve cover gasket?
sometimes the valve cover gasket just needs a small amount of ‘snugging’ up of the bolts.
If the engine is worn out then nothing may stop them.
It might help to know what kind of car you’re talking about and how many miles are on it.
Seriously though take your pick at the autoparts store and pray to your favorite deity.