Have a '72 Chevy Pick-up, (350, manual 4-speed), w/ just over 100K miles. Drove it on a regular basis, (not every day), for years, then parked it 3 years ago, (it was used occasionally and I started it on a weekly basis at first, but then got lazy/negligent…). It did not use or leak oil when used regularly, now leaks, (under the engine and engine itself is dirty). I assume seal(s) dried out while it was sitting around. Question: Should I Stop Leak it now, or let it go. I was told that Stop Leak “moistens” the seals to stop leaks, but it also starts to degrade them, eventually resulting in a flood or no sealing effect. I intend to keep it around, but will eventually sell it when the use no longer justifies the insurance cost. Finally, is Stop Leak the best product? Thanks in advance.
Take a chance, the goop in a can might help. It may not. You will not be out much either way.
Stop leak swells the seals. Sure, on that vehicle I’d try it for one oil change. If it works, then once the seals are swelled you can stop using it. I’m unaware of any application where stop leak degrades seals.
Basically, some seals dry out and some seals take a “set”, depending on the seal material and application. A “set” is something technically called “cold flow” where the material actually changes shape over time to comply with its surroundings. The compression that maintains the seal is then lost. Sometimes simply retorquing the bolts holding the pieces together works, however that needs to be done with care. Trying to torque a bolt to stop a leak without realizing that it’s a shoulder bolt or bottomed into a blind hole can result in breaking the bolt…then you need to resort to easy-outs and creative language.
In short, if a bolt stops…don’t keep turning!
Is the oil leaking at the rear of the engine? Check the oil pressure sender, located next to the distributor.
You might just go ahead and replace the valve cover gaskets and the oil pan gasket. My experience with additives and very old gaskets is that the leaks get even worse. I bet new gaskets, especially the oil pan gasket, would make a big difference for not much cost.