High mileage oil and RMS leak

[R49]

Hello all,
My TJ had a slight rear main seal leak.
I took the advice from others here on the forums and tried a high mileage oil.
I used Valvoline High Mileage synthetic blend as I couldn’t find a non-synthetic oil.
After the first wheeling trip, just one small drip on the garage floor.
Now after about 500 miles the leak is completely gone.
My TJ is hardly high mileage at 48,000 miles but it is high in years.
I’ll update if the leak returns.

 

[bbaldwin237]

I found a Pennzoil high mileage conventional and tried that plus a bottle of AT-205. Unfortunately, it didn't seem to fix mine. It's a small leak and I'm not terribly concerned about it at this point. It never actually drips, just builds up to a drop on the bottom of the bell housing. Trying to decide if I have the courage to tackle it myself next summer. But don't really want to do it lying on my back.

 

[Jerry Bransford]

High Mileage engine oils are not miracle workers if the seal is damaged beyond being restored or not seated properly.

 

[Rut Row]

High Mileage engine oils are not miracle workers if the seal is damaged beyond being restored or not seated properly.

agree but most leaks aren't from damage. It is well worth the money to throw in a can of BlueDevil Rear Main Sealer as a diagnostic.

 

[Rut Row]

I left my oil in for 30,000 miles (high mileage) and mine still leaked.

add some BlueDevil Rear Main Sealer. I still had a leak a month after switching to high milage oil and the leak stopped two weeks after adding BlueDevil.

 

[KennethS]

After reading the posts on this subject a while back, I tried Mobil 1 High Mileage on the last oil change. For the past 20 years I have used Mobil 1 10W30 and there has been a slight RMS leak. I used Mobil 1 High Mileage in January and there hasn't bee any oil leaking for several months now.

 

[bohuggabee]

Hello all,
My TJ had a slight rear main seal leak.
I took the advice from others here on the forums and tried a high mileage oil.
I used Valvoline High Mileage synthetic blend as I couldn’t find a non-synthetic oil.
After the first wheeling trip, just one small drip on the garage floor.
Now after about 500 miles the leak is completely gone.
My TJ is hardly high mileage at 48,000 miles but it is high in years.
I’ll update if the leak returns.

The big difference of synthetic and non is hydrocarbons. Carbon build up is rather unpredictable without high compression. So lower tolerance engines create carbon strings in various lengths that bond and stuff. Synthetic blends are not bad. Full synthetics though, if you have driven long periods on pure carbon oil can cause issues. You want to break down the build up as slowly as you built it up... you will always have carbon deposits with hydrocarbons in oil but the blends displace them in colder areas. Thats why they help seal. Leaks inherently are colder. Build carbon? You have a seal! At the same time. That build up will grow where the carbon isnt oxidized or heated to displace. Thats when they start bonding like tempering steel and bluing it. Thats all this is. You are trying to keep your engine blued but not build too much carbon as well.

 

[TheBoogieman]

The big difference of synthetic and non is hydrocarbons. Carbon build up is rather unpredictable without high compression. So lower tolerance engines create carbon strings in various lengths that bond and stuff. Synthetic blends are not bad. Full synthetics though, if you have driven long periods on pure carbon oil can cause issues. You want to break down the build up as slowly as you built it up... you will always have carbon deposits with hydrocarbons in oil but the blends displace them in colder areas. Thats why they help seal. Leaks inherently are colder. Build carbon? You have a seal! At the same time. That build up will grow where the carbon isnt oxidized or heated to displace. Thats when they start bonding like tempering steel and bluing it. Thats all this is. You are trying to keep your engine blued but not build too much carbon as well.

• Sep 8, 2023

 

[Obi-Wan]

Digging up threads that are years old to say we need to keep our engines blued.....