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What seals do HM oils condition?

Posted By: buster

What seals do HM oils condition? - 10/11/18 12:02 AM

The most common engine seals that eventually seems to leak are the rear main and valve cover gasket. What other seals would a HM oil help prevent leaks in?

Rear main,
Crank Seal
Front/Rear CAM seals
OCV?

It won't have an impact on valve cover.

Posted By: The Critic

Re: What seals do HM oils condition? - 10/11/18 12:08 AM

HM oil is unlikely to have any impact on surfaces that were sealed using RTV.

I would expect it to have an impact on all other seals/gaskets though.
Posted By: buster

Re: What seals do HM oils condition? - 10/11/18 12:33 AM

Originally Posted by The Critic
HM oil is unlikely to have any impact on surfaces that were sealed using RTV.

I would expect it to have an impact on all other seals/gaskets though.


cheers
Posted By: anndel

Re: What seals do HM oils condition? - 10/11/18 12:57 AM

Front main seal
Posted By: Warstud

Re: What seals do HM oils condition? - 10/11/18 01:46 AM

Any that are rubber.
Posted By: Snagglefoot

Re: What seals do HM oils condition? - 10/11/18 01:49 AM

I imagine the front seal and rear main seal are most important and the rear main seal is the hardest to replace.
Posted By: dwendt44

Re: What seals do HM oils condition? - 10/11/18 04:08 AM

Hopefully the valve seals would benefit from HM oils as well and the
front and rear crank seals.


My 2¢
Posted By: VeryNoisyPoet

Re: What seals do HM oils condition? - 10/11/18 04:29 AM

Originally Posted by dwendt44
Hopefully the valve seals would benefit from HM oils as well and the
front and rear crank seals.
My 2¢


I've used high mileage oils from Pennzoil, Castrol, Mobil 1, and Valvoline for the past 30k miles. In that time, the puff of blue smoke on startup from weak valve seals has gone from significant down to almost non-existent. When I had the intake manifold off this spring I could see a tiny bit of oil seeping down the valve stems, but apparently that's not enough to make any visible smoke when it fires up. I did have a rear cam seal start to weep this winter, but that may have been previously weakened when the pcv system failed and pressurized the crankcase a few years back. I know it puked oil from the top end when that happened.

Don't have good data on overall oil consumption with HM vs non-HM since the car had slow leaks of various nature from hoses and places other than seals up until this year when I fixed the last of the problems. This oci it's using about 1 quart in 5k miles.
Posted By: SavagePatch

Re: What seals do HM oils condition? - 10/11/18 05:10 AM

What about Spark Plug Tube Seals?
Posted By: LEADED

Re: What seals do HM oils condition? - 10/11/18 10:07 AM

This is 2018 , most Seals nowadays are VITON , not your 1970 rubber different Materials are used in sealing aModern engine . I use Hi Milage oil in lawn Tractor .
Posted By: RyanY

Re: What seals do HM oils condition? - 10/11/18 10:54 AM

Originally Posted by LEADED
This is 2018 , most Seals nowadays are VITON , not your 1970 rubber different Materials are used in sealing aModern engine . I use Hi Milage oil in lawn Tractor .


Good point, but when did this start? HM oil cut down consumption in my 2007 from 1qt/1k to about half a qt/5k. I don't know what it is doing but it is doing it well.
Posted By: MolaKule

Re: What seals do HM oils condition? - 10/11/18 12:19 PM

Originally Posted by MolaKule
When discussing seals such as in engines, transmissions, and other driveline components, the context is that of using flexible, elastomeric materials to keep fluids contained within the mechanical system that have rotating components exiting the system, such as protruding rotating shafts.

For a gasket, the context is that of using a material (such as silicone or cork or composite), or some other material to keep fluids contained in and around stationary objects, such as the valve cover gasket on an engine or the pan gasket on an automatic transmission.


Both seals and gaskets "prevent" loss of fluids...


Conditioning seals refers to the following actions:

Seal swell due to Seal elastomer molecular replacement
Seal cleaning,
.
Posted By: jongies3

Re: What seals do HM oils condition? - 10/11/18 06:44 PM

I personally don't think they do anything different than non high mileage oils. I personally think HM is just a marketing term. I've never noticed a difference in stopping oil leaks or reducing burn off with HM and standard conventional oil. Never tried HM synthetics but I imagine the results would be similar. Another thing to consider is if HM oils are such a great thing, why are there no diesel HM oils? Diesel engines typically outlast gas engines by almost double the mileage so why don't we see things like Rotella, Delo or Delvac HM brews? Food for thought.
Posted By: DONWATERS

Re: What seals do HM oils condition? - 10/12/18 12:25 AM

I think HM oils are all on the thicker side of the stated viscosity which may cut down on leaks also. I also believe that conventional oil is always better at slowing leaks than synthetic given the same weights.
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