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High mileage oil and stop leak, does it shorten a seals life?

As the title states. Can anyone conclusively say that stop leak additives or high mileage oils actually shorten a seals life due to the seals swelling too much or becoming too soft? Also are additives like this harmful to a turbo car, can these additives affect the longevity of the seals or bearing in the turbo or cause deposits?

If one is resorting to high mileage oil and stop leak the life of seals are already on the short side of life. If oil usage and leaks reduce or stop, just drive on,

Exactly. Engine is already on its way out. I can’t imagine how anyone will have facts about the impact on remaining seal life.

These additives can sometimes have their place…for instance to try and mitigate fluid losses while you drive to the place you are going to perform the proper repairs…(Maybe). Just like @“VOLVO V70” states…those seals are already worn out. These products tend not to really work on the average.

When rubber seals start leaking…if they are not physically cracked or damaged…the rubber hardens…these products seek to re-emulsify that rubber in hopes of gaining a seal again. This is all temporary…because even if it works for a little while…once those agents stop working the rubber will then return to the same state if not much worse than before.

I avoid these products like the plague to be honest…why bother when I can simply renew whichever seal we are discussion without too too much effort. Its sort of just “How it goes”

Machines dont like to leak any of their vital fluids…


Here’s the question reposed:

Would it be harmful to use stop leak additives or high mileage oils in an engine with new or nearly new seals, etc.?

High mileage oils that meet API etc. specs (SN) are certainly OK.
All the other “miracle in a can” things, a crap shoot.
As the previous posters are saying since all these products come at extra cost they are almost never used unless there’s a problem.

My seals havent started leaking yet but I’m aproaching 70k miles which is why I was asking if the leak stopping additives can shorten the life of the seals or hurt the turbo bearing and its seals.

I bought a new Oldsmobile Cutlass in 1978. I drove the car 240,000 miles and kept the car for 33 years.It never leaked oil and the only thing that ever went in the crankcase was the 10W-30 oil specified in the owner’s manual. If you aren’t leaking oil, you don’t need “high mileage” oil or oil leak additives. 70,000 miles is not high mileage. Drive on and quit worrying about future problems

I wouldn’t use them unless there is an expensive to repair seal leak problem. Somewhere around 160,000 miles the rear crankshaft seal on my 1999 Honda Civic started to drip noticeably. Since then I have used an anti-leak additive, or high mileage oil that purports to do the job. The leak has diminished. I replace the cardboard in the garage along with the oil and filter every 6 months.

From what I understand, this seal can be replaced only if the engine or trans are removed. So that job will likely never be done unless the leak becomes much, much worse or I need a new clutch. The original clutch is still good after 17 years of service.

Is this for the 2010 Evo that had the engine rebuilt last month?

These additives are not a prophylactic treatment. They are only used after a problem surfaces. What do you think will happen if you take a normally functioning seal and swell its size?

If you need to use a seal swell product to seal a leak, and it seals the leak, how is that shortening the life, unless you planned on adding fluid and not using the seal swell, then yes it may shorten the life as you may experience a massive blowout of the seal vs constantly adding fluid.

Time frame who knows. Sure the proper repair is a new o-ring or whatever, but bandaid seal swell can get you by, for a while.

“Drive on and quit worrying about future problems.”

My sentiment exactly.

If you need to use a seal swell product to seal a leak, and it seals the leak, how is that shortening the life,

He’s talking about using it BEFORE it starts leaking as a preventive measure…

If the OP is talking about using additives before they might be necessary I just don’t think putting things like that in just for heck of it is a good idea. What about the if it ain’t broke don’t fix it thought !

Additives can be great for extending the life of an old worn engine… when they work, and they sometimes do. They’re well worth the few bucks to try if proper repair or replacement is uneconomical. They don’t shorten the life of seals, they allow you to get a bit more life out of them when they’re shot.

There’s an old axiom that I like: “keep a good car running perfectly, but just keep a worn out car running”. Additives can be great for the latter goal. They’re not very good for the former.