WaIIy wrote:
I have Mercruiser 5.7's 1989 and boat on Lake Erie near Cleveland.
My mechanic recommends straight 30wt oil and that's been fine, today he
said a new bulletin came out from Mercury and it was something like 30
wt up to 60 degrees F and 40 wt for over 60 degrees F.

Now my mechanic says to use straight 40 weight.

What do you think?

Use the 40, if that's the recommendation.

The multigrade oils only thicken up when they get really hot (various
additives, plastics etc expand & change as the temp rises, but the base
oil is the lower claim, so a 20-40 is actually 20 grade oil with
additives to help when it gets hot), as in a properly thermostatted car
engine.

The trouble or one of the troubles:-) with raw water cooled engines is
they can't run the normal high (near boiling temp) thermostats, so the
engine & therefore oil might not get really hot & if it were multigrade
it "might" not thicken enough to give the engine proper protection when
worked hard.

Other end of the scale; some boat engines, skiing or heavy cruisers can
really put the engine to work & although the raw water low temp thermo
cools the block, still & all the oil can get hot, again 40 is better
than 30 in that case too.

K

On Wed, 06 Oct 2004 05:40:04 GMT, WaIIy
wrote:


I have Mercruiser 5.7's 1989 and boat on Lake Erie near Cleveland.
My mechanic recommends straight 30wt oil and that's been fine, today he
said a new bulletin came out from Mercury and it was something like 30
wt up to 60 degrees F and 40 wt for over 60 degrees F.

Now my mechanic says to use straight 40 weight.

What do you think?

Karen has pretty much hit it. Straight 40 weight if that's what the
manufacturer recommends.

However, you might want to discuss with him the age of the motor and
if it's lasted this long on the 30/40 combination, then why not stick
with it?

Later,

Tom
-----------
"Angling may be said to be so
like the mathematics that it
can never be fully learnt..."

Izaak Walton "The Compleat Angler", 1653

Short Wave Sportfishing wrote:




Karen has pretty much hit it. Straight 40 weight if that's what the
manufacturer recommends.


Tom

Multigrade oils do not "thicken up" when they get hot, hotter, or really
hot.

Rob

On Wed, 06 Oct 2004 10:04:00 -0400, trainfan1
wrote:

Short Wave Sportfishing wrote:




Karen has pretty much hit it. Straight 40 weight if that's what the
manufacturer recommends.


Tom

Multigrade oils do not "thicken up" when they get hot, hotter, or really
hot.

I understand that. I agreed with Karen on her statement about the
manufacturer's recommendations.

I thought that was pretty evident.

Take care.

Tom

"The beatings will stop when morale improves."
E. Teach, 1717

trainfan1 wrote:
Short Wave Sportfishing wrote:




Karen has pretty much hit it. Straight 40 weight if that's what the
manufacturer recommends.



Tom


Multigrade oils do not "thicken up" when they get hot, hotter, or really
hot.

Rob

I agree Rob it was a bad turn of phrase & I apologise.... again:-)

The main thing is that in multi grade oils the actual oil (before
additives etc) is the lower of the grades, so it will (deliberately)
stay thinner at lower temps.

As for the rest..... hmmm the way the price of oil is going it won't
matter much soon.

Thanks for the whack behind the ear; I deserved it:-)

I just got overly excited about an on topic post:-)

K

On Fri, 08 Oct 2004 18:10:53 +1000, "K. Smith"
wrote:

trainfan1 wrote:
Short Wave Sportfishing wrote:




Karen has pretty much hit it. Straight 40 weight if that's what the
manufacturer recommends.



Tom


Multigrade oils do not "thicken up" when they get hot, hotter, or really
hot.

Rob

I agree Rob it was a bad turn of phrase & I apologise.... again:-)

The main thing is that in multi grade oils the actual oil (before
additives etc) is the lower of the grades, so it will (deliberately)
stay thinner at lower temps.

As for the rest..... hmmm the way the price of oil is going it won't
matter much soon.

Thanks for the whack behind the ear; I deserved it:-)

I just got overly excited about an on topic post:-)

I feel your pain. :)

Take care.

Tom

"The beatings will stop when morale improves."
E. Teach, 1717

ignore K's advice in its entirety, for K's has shown herself to be utterly
ignorant in the subject with this line:

The multigrade oils only thicken up when they get really hot

read the whole thing if you can stomach it.

"K. Smith"
Date: 10/6/2004 5:48 AM Eastern Daylight Time
Message-id:

WaIIy wrote:
I have Mercruiser 5.7's 1989 and boat on Lake Erie near Cleveland.
My mechanic recommends straight 30wt oil and that's been fine, today he
said a new bulletin came out from Mercury and it was something like 30
wt up to 60 degrees F and 40 wt for over 60 degrees F.

Now my mechanic says to use straight 40 weight.

What do you think?

Use the 40, if that's the recommendation.

The multigrade oils only thicken up when they get really hot (various
additives, plastics etc expand & change as the temp rises, but the base
oil is the lower claim, so a 20-40 is actually 20 grade oil with
additives to help when it gets hot), as in a properly thermostatted car
engine.

The trouble or one of the troubles:-) with raw water cooled engines is
they can't run the normal high (near boiling temp) thermostats, so the
engine & therefore oil might not get really hot & if it were multigrade
it "might" not thicken enough to give the engine proper protection when
worked hard.

Other end of the scale; some boat engines, skiing or heavy cruisers can

really put the engine to work & although the raw water low temp thermo
cools the block, still & all the oil can get hot, again 40 is better
than 30 in that case too.

K

mercruiser does not build engines, it assembles marine systems. ask the
manufacturer of the engine for its advice, and then go with the 20w-40 it
recommends. Then replace your mechanic, or be prepared to spend some money
with him

I have Mercruiser 5.7's 1989 and boat on Lake Erie near Cleveland.
My mechanic recommends straight 30wt oil and that's been fine, today he
said a new bulletin came out from Mercury and it was something like 30
wt up to 60 degrees F and 40 wt for over 60 degrees F.

Now my mechanic says to use straight 40 weight.

What do you think?

On 06 Oct 2004 12:04:58 GMT, (JAXAshby) wrote:

mercruiser does not build engines, it assembles marine systems. ask the
manufacturer of the engine for its advice, and then go with the 20w-40 it
recommends. Then replace your mechanic, or be prepared to spend some money
with him

Where did you find GM's reccomendation of 20w-40 oil for a marinized
engine in a marine application? Can you substantiate that or did you
just pull it out of your ass?

Go with Mercruiser's reccomendation. And Karen's advice is correct.

I'm using Amsoil 15-40 marine diesel in my 1987 5.7 liter and am happy
with it so far. Ask me whether I'm still happy in 2500 hours.

Capt. Jeff