Any leaks if I stop using synthetic high mileage oil?

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Been using Royal Purple HMX 5w-30 in a Toyota 3.4 V6 and a Chevy 5.7 LS1. Both have just over 130k miles. The 3.4 doesn't leak any oil, but the LS1 only seeps from the timing cover. Both engines are extremely clean with almost no varnish on the heads, and don't consume oil.

Will both these engines end up leaking from every other seal if I switch to a normal Synthetic 5w-40? I know high mileage oil has seal swellers, and my engines are over 15 years old. I'd really like to get them off the high mileage deal, but if need be, do I have to stick with HM forever? Tell me your experience if you ever got an oil leak switching from an HM oil.

From what I researched, these engines use thicker oils overseas than the US, and 5w-40 add-packs are more potent, kinda like high mileage oil. I drive my vehicles briskly here in Tucson where temps can go over 110. I've seen oil temps rise above 220 lol, so 5w-40 is sounding pretty good.
 
I see no reason why you'll get leaks changing oil weights.

Always wanted to try the Royal Purple HMX ...
 
It's not like they're kicking a crack habit and need to be weaned off, just stop using it....‚ But firstly, why do you feel compelled to stop using a HiMi formula? For all you know it's why your NOT pizzing oil all over the place. ...
 
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Originally Posted by CT8
Why change?

Lately been contemplating the use of a cheaper 5w-40 instead. HMX is like $10 a quart, and I change it out before the 12K interval it's rated for because I live in dusty conditions. 7.5k on the Toyota and 5k on the Corvette.

Guess I can't fix what ain't broken. A lot of 5w-40 oils I found are for modern European vehicles and diesels anyway. Royal Purple has an ordinary 5w-40 with Synerlec, but it's the same price as HMX. Looks like I'm better off just sticking to what's been working so great.
 
Originally Posted by Loobit
Originally Posted by CT8
Why change?

Lately been contemplating the use of a cheaper 5w-40 instead. HMX is like $10 a quart, and I change it out before the 12K interval it's rated for because I live in dusty conditions. 7.5k on the Toyota and 5k on the Corvette.

Guess I can't fix what ain't broken. A lot of 5w-40 oils I found are for modern European vehicles and diesels anyway. Royal Purple has an ordinary 5w-40 with Synerlec, but it's the same price as HMX. Looks like I'm better off just sticking to what's been working so great.

Can't argue with that. But would it be beyond the realm of possibilities to try a 5w30 HM formula from another less expensive but equally good brand like a M1 or Pennzoil???
 
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The LS1 might seep a bit more, operative word is might. If the other engine wasn't leaking there is no reason why it should start leaking now. I'd try it, that's the only way to know for sure.
 
Undamaged gaskets don't leak. I hold the opinion that a leak needs a new gasket. Where the base stock comes from doesn't matter, you either have good gaskets or bad gaskets.
 
Like what was mentioned before - there is a seal conditioner in high mileage oil so it is not swelling them. Secondly, what you have been doing is working so maybe no need to change. I also understand from reading and oil maker websites that HM oil also has a little stronger additive package to help older engines stay cleaner and fight blow by etc. This little more protection is a bonus over the non HM formulas.
 
Originally Posted by GMBoy
Like what was mentioned before - there is a seal conditioner in high mileage oil so it is not swelling them. Secondly, what you have been doing is working so maybe no need to change. I also understand from reading and oil maker websites that HM oil also has a little stronger additive package to help older engines stay cleaner and fight blow by etc. This little more protection is a bonus over the non HM formulas.

Exactly! Look for a cheaper HM oil.
 
There have been many discussions on here over the years. Some believe its just "conditioners". I believe in addition to conditioners there is a swelling agent. I read firsthand example after example of the words "sweller" and "swells seals" being used by XOM employees answering questions in the M1 FAQ (recently merged, deceased). Also, the obvious. Leaks come back when you stop using HM oil. If its just conditioners like regular motor oil, the leaks would not return. IMO the word conditioners is used because its softer, not to scare people out of buying product. Pat Goss is right IMO. He says don't use HM oil unless you need to. Because of the swelling. It can hurt valve seals which rub against the stem. Google his video.

To answer your question, being someone who has experimented back and forth... If you slowed or stopped leaks using high mileage oil, the leaks will return around 500-1k miles. When the seals shrink. You can try a different HM oil thats cheaper. I use ST HM. works pretty good on the leaky Maxima. If you used HM oil because you have high mileage, no leaks, shifting away from it might have no side effects.
 
Pat Goss is about 40 years behind the times. Rear main seal seep did not return after changing back from HM to regular oil on my F150.
 
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Originally Posted by LeakySeals
There have been many discussions on here over the years. Some believe its just "conditioners". I believe in addition to conditioners there is a swelling agent. I read firsthand example after example of the words "sweller" and "swells seals" being used by XOM employees answering questions in the M1 FAQ (recently merged, deceased). Also, the obvious. Leaks come back when you stop using HM oil. If its just conditioners like regular motor oil, the leaks would not return. IMO the word conditioners is used because its softer, not to scare people out of buying product. Pat Goss is right IMO. He says don't use HM oil unless you need to. Because of the swelling. It can hurt valve seals which rub against the stem. Google his video.

To answer your question, being someone who has experimented back and forth... If you slowed or stopped leaks using high mileage oil, the leaks will return around 500-1k miles. When the seals shrink. You can try a different HM oil thats cheaper. I use ST HM. works pretty good on the leaky Maxima. If you used HM oil because you have high mileage, no leaks, shifting away from it might have no side effects.

Leaks come back because you have a failing seal not because of some deficiency or flaw in the HiMi oils chemistry. You have to have realistic expectations...stop leak additives aren't intended to be a permanent fix for seal failure, they're a band aid to keep worn, hardened seals in service when the seal has effectively reached the end of it's service life.

If a leak returns after stopping use of a HiMi formula or OTC stop leak additive the oil or additive hasn't failed, you are simply on borrowed time with respect to that seal. At which point you have two options.. either a) replace the leaking seal or b) continue to use stop leak until catastrophic failure occurs.
 
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Originally Posted by Mad_Hatter
Originally Posted by LeakySeals
There have been many discussions on here over the years. Some believe its just "conditioners". I believe in addition to conditioners there is a swelling agent. I read firsthand example after example of the words "sweller" and "swells seals" being used by XOM employees answering questions in the M1 FAQ (recently merged, deceased). Also, the obvious. Leaks come back when you stop using HM oil. If its just conditioners like regular motor oil, the leaks would not return. IMO the word conditioners is used because its softer, not to scare people out of buying product. Pat Goss is right IMO. He says don't use HM oil unless you need to. Because of the swelling. It can hurt valve seals which rub against the stem. Google his video.

To answer your question, being someone who has experimented back and forth... If you slowed or stopped leaks using high mileage oil, the leaks will return around 500-1k miles. When the seals shrink. You can try a different HM oil thats cheaper. I use ST HM. works pretty good on the leaky Maxima. If you used HM oil because you have high mileage, no leaks, shifting away from it might have no side effects.

Leaks come back because you have a failing seal not because of some deficiency or flaw in the HiMi oils chemistry. You have to have realistic expectations...stop leak additives aren't intended to be a permanent fix for seal failure, they're a band aid to keep worn, hardened seals in service when the seal has effectively reached the end of it's service life.

If a leak returns after stopping use of a HiMi formula or OTC stop leak additive the oil or additive hasn't failed, you are simply on borrowed time with respect to that seal. At which point you have two options.. either a) replace the leaking seal or b) continue to use stop leak until catastrophic failure occurs.


I'm not sure what you mean. I have real expectations of high mileage oil. I only use it when I have a leak or when I'm consuming oil. And the vehicle is too old to fix not worth fixing. I don't expect it to fix anything.
 
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