I
am not sure why I am not just running 30HD.

because 30w does not lube pressure oil bearings as quickly upon engine startup
as does 5w-40. Not by a long shot. you can hear the difference, easily.

because 30w does not lube pressure oil bearings as quickly upon engine
startup
as does 5w-40. Not by a long shot. you can hear the difference, easily.

My point is Merc says to use 10w-30 OR 25W-40. (the only grades they sell)
30HD seems to be right in the middle.
Merc doesn't make 30HD and I suspect that has more to do with the recomendation
than anything.
I do know their 10W-30 is breaking down after 20 hours and I am losing oil
pressure. That is not a good thing.

Before you ask, no they don't have any answers ... I asked.

My point is Merc says to use 10w-30 OR 25W-40. (the only grades they sell)
30HD seems to be right in the middle.
Merc doesn't make 30HD and I suspect that has more to do with the
recomendation
than anything.

Merc doesn't make any oil, it merely repackages it (or more accurately, it has
it repackaged for them).

straight weight oils have not be recommended by major engine manufacturers (of
these kinds of engines) for a couple decades. multi grade oils were developed
to give better lubrication upon engine startup while still giving proper
lubrication at operating termps and loads.

Merc doesn't make any oil, it merely repackages it (or more accurately, it
has
it repackaged for them).

Exactly why I wonder if all of the "automobile" advice applies to marine
outboards. This is oil made for the auto industry where the "starting" range is
0f or below to a normal operating temp of over 210f (what most auto thermostats
run).
That is an operational range of 200 degrees or so.
Outboards seldom start below 70f and it is closer to 80 most of the time here.
The thermostat is 120f.

start your engine from cold (whatever temp you happen to be standing in) 30w
oil. Listen to the sounds you engine makes. notice the difference in sounds
coming from the engine over the next 30 to 60 seconds. shut down your engine
and restart, listening to the sounds.

The sounds you hear first that went away in a minute or so is the sounds made
by engine bearings lacking in pressure oil

Now, do the same with 10w-40 and listen again.

end of report.

Merc doesn't make any oil, it merely repackages it (or more accurately, it
has
it repackaged for them).

Exactly why I wonder if all of the "automobile" advice applies to marine
outboards. This is oil made for the auto industry where the "starting" range
is
0f or below to a normal operating temp of over 210f (what most auto
thermostats
run).
That is an operational range of 200 degrees or so.
Outboards seldom start below 70f and it is closer to 80 most of the time
here.
The thermostat is 120f.

Greg wrote:
because 30w does not lube pressure oil bearings as quickly upon engine
startup
as does 5w-40. Not by a long shot. you can hear the difference, easily.


My point is Merc says to use 10w-30 OR 25W-40. (the only grades they sell)
30HD seems to be right in the middle.
Merc doesn't make 30HD and I suspect that has more to do with the recomendation
than anything.
I do know their 10W-30 is breaking down after 20 hours and I am losing oil
pressure. That is not a good thing.

Before you ask, no they don't have any answers ... I asked.

I still wonder if my Atomic-2 engine would work better, or longer,
if the recommended 10w oil was replaced by 10-30?

My oil pressure goes from 20# cold to 7 or 8 when warmed up to the
"warm" range. I have no thermostat, so the engine is always working
'cool.' Plugs carbon up, I don't care, they are still cheaper than
gas and easily replaced, but my valve guides, piston tops, etc, are
all black, I suspect.

All I want is to get to and from a mooring with reliable backup if
the sailing or current puts me onto the nearby rocks, and the
occasional one day voyage sometimes under power as the times
require, to and from the cottage and the ramp.

Terry K

I still wonder if my Atomic-2 engine would work better, or longer,
if the recommended 10w oil was replaced by 10-30?


10w oil was not the recommended oil, but rather 30w. and yes, it will last
longer if you use 10w-30, unless you start it and run it for hours on end on
end on end on end on end on end on end on end on end on end on end on end on
end on end on end on end on end on end on end on end on end on end on end on
end on end on end on end on end on end on end on end on end on end on end on
end on end...