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Discussion Starter #1
So the time has come for me to change the oil in my Focus. The car already has about 81000 miles on it, so my thinking is that sticking with convetional oil would be better and switching to synthetic would be pointless now.
 

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Really? I thought I read somewhere that unless you begin using it early in the cars life (idk, 10000 miles or less), you will not really see many of the benefits.
 

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It's sort of like a person eating a good diet. If you start eating a better diet late in your life, you miss out on a lot of the benefits. But it still is a good idea.

Note that the following comment is widely debated, with some people saying it is true, and others saying it is pure hogwash. You'll have to make up your own mind on this one... I only post it so you are aware the concern exists.

Some people have noted that switching to synthetic after using dino oil for many miles and time, they seem to have more oil leakage. This is not completely unexpected, as the synthetic stuff generally does "flow better" and tends to leak more than the dino stuff and find its way through smaller passages. So it is debatable as to whether the switch to synthetic actually messes with the seals (as it did in the past), or if it simply is a case that synthetics more easily leak through whatever "leak spots" already exist.

In the past (1970/80s), this was clearly true, as many older seals tended to "swell" a bit in the presence of dino oil, but not with synthetic oil. As a result, a switch to synthetic would, in essence, shrink some seals, causing leaks. This mechanism is no longer the case, as (1) newer seal materials are designed with synthetic oils in mind, and (2) synthetic oils have been reformulated to have some additives which provide similar "seal swelling" characteristics to dino oils.

But, FWIW, some people do still report increased leakage when making the switch on higher milage engine.
 
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