Moisture is one of the problems with all oils, synthetic or regular. As an
engine runs, combustion blowby into the crankcase contaminates the oil with
moisture, soot and unburned fuel. Moisture is the worst culprit because it
forms acids and sludge. The oil itself never wears out but the additives do
that give oil it's special lubricating properties.

To me synthetics seem to not break down as fast from the moisture, and
contaminates. Synthetics seem to not absorb moisture as do regular oils
from sitting. After the hurricane season is finished I always change the
lubricants on the boats.

Jack

"Tony Thomas" wrote in message
news:uYL0b.207335$o%2.95079@sccrnsc02...
Mercury claims that you don't want to use synthetic because it has a
higher
tendency to absorb moisture. As an engine sits for long periods of time,
moisture/condensation can/will be absorbed by the oil and fuel. In this
case, since most boats tend to sit for 1, 2, or 3 weeks at a time between
use, you tend to absorb more moisture in the oil which reduces the oils
ability to do its job. Once you run the engine for a while, the moisture
is
burned off. But during this warmup period they claim you get less
lubrication than with regular oil.

At least that is their claim.
Someone else will have to figure out if they are right or not.

Now, if you use the boat for commercial purposes, it does not sit any
longer
than a car and everything changes.

--
Tony
My boats and autos - http://t.thomas.home.mchsi.com



"JG" wrote in message ...
I have been told that automotive synthetic oils (Mobil 1) should not be
used in a marine engine. I didn't hear the reasoning behind this
statement.
Does anyone know why they should not be used?

Thanks JG




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