Castor Oil for rear main seals?

[Dave1027]

Recently saw a Youtube claiming castor oil could be used to restore leaking rear main seals. It states it cannot fix a leak from a cracked or torn seal. Only a seal that has shrunk to the point it no longer can seal.. It said to add 2 ounces/qt of motor oil. Castor oil seems like a benign additive to use. Even if it didn't work, I don't see how it could do any harm to try. Anybody ever tried this or heard about it?

 

[GMBoy]

Hard pass here. Caster oil will not tolerate inside an engine and won't do anything but turn into a deposit inside your engine.

 

[Hirev]

Oh jeez that youtube has no clue. Used Castor oil (bean oil) on a 2 stoke dirt bike in the 1970s i learned my lesson that stuff.... it is nasty.

 

[Japanese]

Recently saw a Youtube claiming castor oil could be used to restore leaking rear main seals. It states it cannot fix a leak from a cracked or torn seal. Only a seal that has shrunk to the point it no longer can seal.. It said to add 2 ounces/qt of motor oil. Castor oil seems like a benign additive to use. Even if it didn't work, I don't see how it could do any harm to try. Anybody ever tried this or heard about it?

I completely agree with the people above. Castor oil makes mess inside the engine and its use is justified only in racing applications where people put apart the engine after each race and thorrowly clean its internals.
Also, as far as I know, without any solvents (like gasoline in 2-stroke applications) castor oil won't mix well with other oils, regardless if they are conventional or synthetic. Castor oil cannot be or it's not recommended to be used below 35°F. In low temps. and larger amounts it cannot get in suspension even with gasoline, which is one of the best solvents.

Here I briefly outlined several properties of the castor oil:
https://bobistheoilguy.com/forums/threads/castrol-is-bringing-back-r40-castor-racing-oil.403605/#post-7571928

 

[JunkdrawerDog]

Castor oil makes mess inside the engine and its use is justified only in racing applications where people put apart the engine after each race and thorrowly clean its internals.

It was tolerable in racing two strokes because the engine was always apart for one thing or another before the castor could get it totally gummed up.

 

[Japanese]

Recently saw a Youtube claiming castor oil could be used to restore leaking rear main seals. It states it cannot fix a leak from a cracked or torn seal.

If you have rear main seal leak, use Valvoline MaxLife (synth blend or full synth) or Valvoline Restore & Protect and will help it.
Also, don't fill up the oil to the max on the dipstick—keep it midway or a bit over the middle.

 

[AdmiralYoda]

I used my old oil after cooking bacon. I find it thickens the oil up and helps seal all the leaks. Takes it up a grade. Smells good too.

 

[DCDG]

isn't castor oil rubber safe and doesn't cause swelling? its the main product in sil-glyde.

 

[fantastic]

If there was a lip inside the seal one could put high temp grease inside but a lot of seals don't have that groove.

 

[f355spider]

Recently saw a Youtube claiming castor oil could be used to restore leaking rear main seals. It states it cannot fix a leak from a cracked or torn seal. Only a seal that has shrunk to the point it no longer can seal.. It said to add 2 ounces/qt of motor oil. Castor oil seems like a benign additive to use. Even if it didn't work, I don't see how it could do any harm to try. Anybody ever tried this or heard about it?

There are threads here about products specifically designed to swell seals and o-rings. I recall a mechanic or two chimed in and said AT-205 and Blue Devil Oil Stop Leak were recommended. They can be used for differentials as well. They said these are not 100% cure alls, but did work many times.

Blue Devil even makes a version specifically for rear main seals. I'm curious how it differs from the Oil Stop Leak version.

 

[shortyb]

Tried both the AT-205 and Blue Devil RMS sealer on a failing rear main for the wagon. Leak slowed but never completely stopped. What DID stop the leak for about 5K was Valvoline MaxLife in the red jug (synthetic blend). Eventually it started dripping again right up until it finally stopped for good with the replacement of the seal.

 

[f355spider]

Project Farm guy tested a bunch of products 3 years ago and measured how much swelling occurs on o-rings.


AT-205 came out on top...but he said any of the top 6 may help.

 

[MolaKule]

Recently saw a Youtube claiming castor oil could be used to restore leaking rear main seals. It states it cannot fix a leak from a cracked or torn seal. Only a seal that has shrunk to the point it no longer can seal.. It said to add 2 ounces/qt of motor oil. Castor oil seems like a benign additive to use. Even if it didn't work, I don't see how it could do any harm to try. Anybody ever tried this or heard about it?

I say it is a bad idea and more internet misinformation.

Pure Castor oil contains glycerin, an oxidant that destroyed many an engine before they separated out the glycerin.

I know of no real seal swelling capabilties of raw castor oil.