I was told from one of the dealerships around my area that after the switch to synthetic the vehicle should not go back to conventional due to the possibilities of engine leakage. He was not that specific where the leaks occurr. Any truth to that theory?
Do synthetics cause leaks
- Thread starter chevydude
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I think with the older PAO based synthetics could leak and may still do so as they are not as compatible with seals or cause them to harden etc. Someone will clarify this im certain. But the addition of seal swell/ester etc combats this in the newer oils. Also i cannot see a difference with a Group 3 synthetic as its a mineral oil still at the end of the day, unless the molecules are changed to make it more leak prone, again one with knowledge will correct or clarify....
About the only way you'll have an engine leak is if you already have one that might be amplified a bit by the smaller molecules. Since it is already there, that is a moot point.
Otherwise you may find yourself in a situation like I was in. I switched over to synthetic this year. I had a small leak that was plugged with some dirt/oxidized oil. When I switched the synthetic washed that away, and oil started dripping onto the exhaust manifold.
Otherwise, most if not all of the good oils today have seal conditioners as additives.
Otherwise you may find yourself in a situation like I was in. I switched over to synthetic this year. I had a small leak that was plugged with some dirt/oxidized oil. When I switched the synthetic washed that away, and oil started dripping onto the exhaust manifold.
Otherwise, most if not all of the good oils today have seal conditioners as additives.
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Depends on gasket material. Both valve cover gaskets on my Mustang began leaking quite heavily when it was switched to Mobil 1. A new set of gaskets fixed it right up.
It's not a myth. It is simply that the situation required for the leaks to occur is not present in a large percentage of vehicles that are changed over.
It's not a myth. It is simply that the situation required for the leaks to occur is not present in a large percentage of vehicles that are changed over.
I've never heard of going from synthetics ---> conventional causing problems (leaks). But on older vehicles (maybe 10 -12 years or older) going from a conventional to PAO (Group IV) based synthetics can cause leaks. PAO's can cause a small amount of seal shrinkage depending on the seal material. This is usually counterbalanced with esters, but … your mileage may vary.
Unless its eating or leaking then yes. It could make it worse, if you have no issues i wouldnt worry about it.
I wouldn't say synthetics cause leaks, they might find them. I look at it this way, in very simplistic terms. Synthetic molecules are more uniform in size, lets say for the sake of argument a synthetic molecule is the size of a golf ball. A dino oil is made up of molecules that are less uniform, meaning their molecules are the size of golf balls with baseball molecules mixed in. They would be less likely to leak because of variations in size, and some larger molecules. Now if the engine has no leaks there is nothing to worry about, if it has the beginning of a leak the synthetic might find its way out. I would think switching back to dino would most likely resolve the problem.
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JMO
Frank D
If you compare a 10w30 syn to a 10w30 mineral oil the syn is a true 30 wt. oil. The mineral oil is a thinner base oil probably a thin 20wt. The syn is therefore in no way thinner than the mineral oil, i would say it's thicker. Generally a thicker oil is less likely not more likely to leak.
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Cork gaskets. Common on 80's vehicles. That's what it seems to cause/enhance leaks with in my experience. Mustang and Lincoln both have rubber valve cover gaskets now.
This experience is exclusively with M1, since I haven't used anything other than it or Amsoil in our engines.
This experience is exclusively with M1, since I haven't used anything other than it or Amsoil in our engines.
Originally Posted By: chevydude
I was told from one of the dealerships around my area that after the switch to synthetic the vehicle should not go back to conventional due to the possibilities of engine leakage. He was not that specific where the leaks occurr. Any truth to that theory?
I went to synthetic oil at 118,000 miles in my 1993 Civic. Now with 260,000 miles, no leaks. My understanding is that I can go back to conventional oil with no worries. Due to my extended experience with synthetic oil and dino oil for that matter, I choose to use synthetic oil exclusively.
I was told from one of the dealerships around my area that after the switch to synthetic the vehicle should not go back to conventional due to the possibilities of engine leakage. He was not that specific where the leaks occurr. Any truth to that theory?
I went to synthetic oil at 118,000 miles in my 1993 Civic. Now with 260,000 miles, no leaks. My understanding is that I can go back to conventional oil with no worries. Due to my extended experience with synthetic oil and dino oil for that matter, I choose to use synthetic oil exclusively.
I think rg200amp has it right.
The early knock on synthetics were that they chemically affected the prevailing seal materials used in the 60s and 70s. On a modern engine, that's now a non-issue, due to advances in the chemistry of both seals and oils.
Folks that develop seal leaks today after going over to a synthetic (and I don't deny that some do experience leaks), are usually suffering partial cleaning of a faux seal - a seal now formed around deposits from conventionals. Synthetics clean up just enough to start a leak. Cleaning out the crankcase (and the seals) first with something more powerful like ARX will reduce that risk. Indeed, ARX notes that leaks may develop during the treatment as the seals are being cleaned by their product, and I have experienced this. But the leaks eventually stop and you have a completely clean seal.
Gaskets are a whole different issue. If you've got a gasket leak with a conventional, you'll have a worse leak on a synthetic. That hasn't changed in the almost 35 years I've been pouring synthetics.
The early knock on synthetics were that they chemically affected the prevailing seal materials used in the 60s and 70s. On a modern engine, that's now a non-issue, due to advances in the chemistry of both seals and oils.
Folks that develop seal leaks today after going over to a synthetic (and I don't deny that some do experience leaks), are usually suffering partial cleaning of a faux seal - a seal now formed around deposits from conventionals. Synthetics clean up just enough to start a leak. Cleaning out the crankcase (and the seals) first with something more powerful like ARX will reduce that risk. Indeed, ARX notes that leaks may develop during the treatment as the seals are being cleaned by their product, and I have experienced this. But the leaks eventually stop and you have a completely clean seal.
Gaskets are a whole different issue. If you've got a gasket leak with a conventional, you'll have a worse leak on a synthetic. That hasn't changed in the almost 35 years I've been pouring synthetics.
If syn oil has superior film strength, and I think it does, the capillary action across a gasket may well pull more syn oil out than it would mineral oil. Thus a similar sized defect in gasket and/or flange will lose more syn than mineral oil.
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Originally Posted By: Volvohead
I think rg200amp has it right.
The early knock on synthetics were that they chemically affected the prevailing seal materials used in the 60s and 70s. On a modern engine, that's now a non-issue, due to advances in the chemistry of both seals and oils.
Folks that develop seal leaks today after going over to a synthetic (and I don't deny that some do experience leaks), are usually suffering partial cleaning of a faux seal - a seal now formed around deposits from conventionals. Synthetics clean up just enough to start a leak. Cleaning out the crankcase (and the seals) first with something more powerful like ARX will reduce that risk. Indeed, ARX notes that leaks may develop during the treatment as the seals are being cleaned by their product, and I have experienced this. But the leaks eventually stop and you have a completely clean seal.
Gaskets are a whole different issue. If you've got a gasket leak with a conventional, you'll have a worse leak on a synthetic. That hasn't changed in the almost 35 years I've been pouring synthetics.
Cork gaskets dry and harden. I imagine they are probably "sealed" on the inside with junk/varnish...etc. The engines I am talking about with my first-hand examples here are a 1987 302HO and a 1989 302. BOTH had factory cork valve cover gaskets. BOTH began leaking VERY heavily a few months after switching to Mobil 1. They may have had VERY mild seepage before that, but it was not observable on the dipstick.
A new set of gaskets fixed things right up. The non-cork gaskets don't seem to be affected in the same way.
Comically, the Lincoln spent a lot of it's early life on M1. When I left home to go to school, dad got lazy and began taking it to a garage to get the oil changed. So it went back on conventional. I switched it back to M1 when I took ownership of it, and in a few months, it was leaking.
I think rg200amp has it right.
The early knock on synthetics were that they chemically affected the prevailing seal materials used in the 60s and 70s. On a modern engine, that's now a non-issue, due to advances in the chemistry of both seals and oils.
Folks that develop seal leaks today after going over to a synthetic (and I don't deny that some do experience leaks), are usually suffering partial cleaning of a faux seal - a seal now formed around deposits from conventionals. Synthetics clean up just enough to start a leak. Cleaning out the crankcase (and the seals) first with something more powerful like ARX will reduce that risk. Indeed, ARX notes that leaks may develop during the treatment as the seals are being cleaned by their product, and I have experienced this. But the leaks eventually stop and you have a completely clean seal.
Gaskets are a whole different issue. If you've got a gasket leak with a conventional, you'll have a worse leak on a synthetic. That hasn't changed in the almost 35 years I've been pouring synthetics.
Cork gaskets dry and harden. I imagine they are probably "sealed" on the inside with junk/varnish...etc. The engines I am talking about with my first-hand examples here are a 1987 302HO and a 1989 302. BOTH had factory cork valve cover gaskets. BOTH began leaking VERY heavily a few months after switching to Mobil 1. They may have had VERY mild seepage before that, but it was not observable on the dipstick.
A new set of gaskets fixed things right up. The non-cork gaskets don't seem to be affected in the same way.
Comically, the Lincoln spent a lot of it's early life on M1. When I left home to go to school, dad got lazy and began taking it to a garage to get the oil changed. So it went back on conventional. I switched it back to M1 when I took ownership of it, and in a few months, it was leaking.
Originally Posted By: jldcol
If you compare a 10w30 syn to a 10w30 mineral oil the syn is a true 30 wt. oil. The mineral oil is a thinner base oil probably a thin 20wt. The syn is therefore in no way thinner than the mineral oil, i would say it's thicker. Generally a thicker oil is less likely not more likely to leak.
There are plenty of 10W30 dino oils that are thicker than their syn counterparts (Mobil 1 vs Clean 5000; Syntec vs GTX). Viscosity isn't the reason that syn may cause leaks.
If you compare a 10w30 syn to a 10w30 mineral oil the syn is a true 30 wt. oil. The mineral oil is a thinner base oil probably a thin 20wt. The syn is therefore in no way thinner than the mineral oil, i would say it's thicker. Generally a thicker oil is less likely not more likely to leak.
There are plenty of 10W30 dino oils that are thicker than their syn counterparts (Mobil 1 vs Clean 5000; Syntec vs GTX). Viscosity isn't the reason that syn may cause leaks.
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