Rick's Free Auto Repair Advice

Engine oil stop leak products

Do engine oil stop leak products work?

How do engine oil stop leak products work?

If you look at the material safety and datasheets for the major oil stop leak products, you’ll see that they’re made from one of two base products: heavy naphthenic or glycol ethers.  Heavy naphthenic products soften hardened rubber seals and gaskets, making them more pliable. Glycol ethers, on the other hand, cause rubber seals and gaskets to soften and swell.

If you’re into chemistry, do a search for the MSDS sheets on these oil stop leak products: Bar’s Engine Oil Stop Leak Concentrate, BlueDevil Oil Stop Leak, LiquiMoly Motor Oil Saver, Lucas Engine Oil Stop Leak, and STP Engine Stop Leak.

engine oil stop leak products

But do oil stop leak products work?

Neoprene is commonly used for valve stem seals, oil filter seals, and in composite cork/rubber gaskets.

Both types of oil stop leak products work well on neoprene gaskets and seals. Over time, neoprene hardens, becomes brittle, and cracks. Both types of oil stop leak products soften the hardened neoprene and glycol ether causes it to swell. That can allow a neoprene gasket to seal again and stop the leak. However, if the leak is due to a round seal on a rotating part, the fix will be temporary since the rotating part will quickly wear out the newly swelled neoprene.

If the leaking seal or gasket is made from a composite of rubber and cork, these oil stop leak products don’t do a very good job of stopping the leak because they have no effect on the cork components and they can dissolve the binding agents that hold the composite materials together.

Does oil stop leak work on silicone gaskets?

Not really. Silicone seals and gaskets are used in automotive applications because they’re highly resistant to degradation from petroleum-based products. Since heavy naphthenic is produced from petroleum, it doesn’t work on silicone seals and gaskets. The same is true with glycol ethers; not very effective on silicone.

Does oil stop leak work on RTV sealer?

No. RTV is a silicone-based product so it has the same resistance to swelling as a silicone gasket or seals. If your RTV sealed valve cover, oil pan or transmission pan was sealed with RTV, none of the oil stop leak products will work.

Should you use oil stop leak products in your engine?

If oil is leaking from a neoprene seal or gasket, you may see relief by using an oil stop leak product. However, if the seal is on rotating parts, the fix will be temporary. If the leak is from a silicone gasket or seal, you won’t see any improvement.

CAUTION: When using an oil stop leak product, you must follow the dosing instructions on the container. More is NOT better. You can cause expensive seal damage throughout the engine by using too much oil stop leak product

©, 2021 Rick Muscoplat


Posted on by Rick Muscoplat

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