<VV> Oil

Ed Gilroy egilroy at gmail.com
Wed Oct 25 19:05:44 EDT 2017

I think what is happening here is a confusion between seals leaking AFTER
converting from dino oil to synthetic vs wearing out due to using synthetic

Synthetic motor oil has identically sized, small molecules. It is
SYNTHETIC, these molecules are manufactured. Dino oil is whatever is
refined, the sizes of the particles vary all over the place. I believe the
real size reference is to the lengths of the "polymer chains".

When you have lots of different sized particles, the big ones tend to dam
up already worn seals. When you change to synthetic, the smaller particles
(all of them the same size) wash out the large particles from the dino oil
and then find their way out past the seals that were already worn and make
it appear the oil caused the leaks, they they were already there, just

So the argument is that changing from dino to synthetic is not a great idea
for a high mileage engine. If you start on synthetic, stay on synthetic.

That is the history to this "story" as I have been informed of.

Small sample size examples:

    My wife has a 2012 Honda CRV with 225K on the clock, I have used Mobil1
0W20 from day one, NEVER put a makeup quart in it and changed it at 7,500
mile interval oil changes. My daily driver is a 2008 Honda Civic with 145K
on it. Mobil1 5W30 from day one, NEVER put a makeup quart in it, ever. same
7,500 mi oil changes. My Harley Tri Glide has 52k miles on it, use Red Line
20W50 Synthetic since day one, NEVER put a makeup quart in it. 5k oil
change interval. My corvair has 120K on it and leaks like a sieve, I use
20W50 dino and add oil just about every other time I drive it!!!


On Wed, Oct 25, 2017 at 6:40 PM, mark--- via VirtualVairs <
virtualvairs at corvair.org> wrote:

> I put 140Kmiles on the rebuilt engine in my 61 Lakewood while using Mobil
> 1. No leaks; no engine problems.
> Mark N
> On 10/25/17 2:25 PM, BBRT via VirtualVairs wrote:
>> I get a LOT of trade publications in the automotive field. Never heard
>> that synthetic oil wears seals, rubber or otherwise.
>> Ethanol affects seals.. Reported numerous times plus other ill effects.
>> VITON seals are great for static seals like o-rings on push rod tubes. Not
>> so good for rotating surfaces.
>> Chuck S
>> -----Original Message-----
>> From: VirtualVairs
>> Sounds like an old wive's tale to me. Can you forward a link to the
>> offending article?
>> ----- Original Message -----
>> From: "Richard"
>> I just read in one of those ASK THE EXPERTS columns that synthetic oil
>> can ultimately wear away rubber seals in the engine.  I know synthetic is
>> better for hotter running engines....I was about to put it in my 66 Monza
>> but now I don't know.     Richard Simoff
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