hi everyone,

I have a 96 sentra with 130K miles in it. I have been using Pennzoil
High mileage 10-40 in it for sometime. I was wondering if it will do
any good if i switched to a semi synthetic or full synthetic. Will this
have any effect on damaging the seals?

Thanks

Rick

Rick wrote:

Rick wrote:
any of the cheapest 10W30 I can find. Don't fall for the marketing fru
ha ha nonsense about high mileage oils etc. Oil is oil. Synthetic is
better, but who really needs it? Actually, you should be using 10W30,
not 40. I use synthetic in my wife's car so I don't have to change the
oil as often. Other than that, I just use regular.

CD

Codifus <codifus (AT) optonline (DOT) net> quipped:

oil change intervals should *never* change just because you're using
synthetic. There's three main purposes for oil (1) lubricate, (2)
cool and (3) suspend/trap foreign particles.

Your engine produces the same amount of contaminants regardless of
the type of oil that's in it. Letting it slosh around for several
thousand more miles than the recommended oil change only allows the
oil to get dirtier and provide less lubrication. Additionally, the
longer the oil is in the engine, the more acids build up.

Synthetic oil is superior to dino oils in every aspect (including
price), however it should never be changed at longer intervals unless
the oil you're purchasing is specifically developed for longer change
intervals. And if you use such longer interval oils, make sure the
oil filter is ALSO made for longer intervals or you're just pushing
dirty oil back through the engine.

"Rick" <rajivs_p (AT) yahoo (DOT) com> wrote

Although there may be those that wouldn't agree, I have been told by several
shops that PUSH synthetic, that to change a car from dino to syn after 100K
often invites OIL LEAKS. Syn oil tends to migrate through seals and those
tiny areas where dino doesn't venture, and often times it seems that older
engines will develop small oil leaks when this change is made. Based on
what I've been told, this is not true for an engine that started using syn
early on, nor is it true for low mileage situations.

Also I note you said you were using 10/40. Unless you're driving in the
desert, (and perhaps not even then) I believe the recommended oil would be
5/30.

Willy

"Willy" <willyk (AT) prodigy (DOT) net> quipped:

*some times".

The reason that *some* cars will leak synthetic oil is that synthetic
oil molecules are uniform in size and tend to be smaller than dino
oil.

Dino oil, OTOH, are not uniform. Like marbles of varying sizes, some
of the molecules are larger than synthetic molecules. So, in the case
of leaks, if the sealed area has a gap large enough for synthetic
molecules to pass through but not the dino oil molecules, you'll get a
leak.

Only in a general sense does that directly relate to the age/mileage
of a car. When a car gets older, tolerances between parts and gaskets
become wider, thus causing leaks...even with dino oil. However, since
only a *portion* of dino oil is small enough to pass through these
"cracks", the effect is not noticed (or so minimal as to not be visual
except under close examination). Synthetic oil, if one molecule can
pass through, ALL of the oil molecules can pass through. Hence the
reason that you'll experience leaks.

Having said that, there's no reason not to switch to synthetic oil and
if the leak(s) are severe, then switch back.

There's no evidence that starting with synthetic oil will guarantee
that future leaks won't occur.

<amstaffs (AT) home (DOT) com> wrote

I agree with you. In fact, just switched my Murano with 105K to syn and
have had no sign of leaks.

Willy