On Wed, 06 Oct 2004 11:15:38 -0400, Slambram
wrote:

On Wed, 06 Oct 2004 10:03:11 -0400, trainfan1
wrote:


Multigrade oils do not "thicken up" when they get hot, hotter, or really
hot. You can demonstrate this in your kitchen today with a quart of
your favorite 10W-40 and a candy thermometer.

This has been a source of endless debates between my friends and i. I
think most people understand multi-viscosity oils on some level, it's
just the terms are confusing. As long as you get that even though the
viscosity rating of a multi-weight oil increases as it gets warmer,
both straight and multi-viscosity oils are actually "thinner" when hot
you've got it.

There you go.

Later,

Tom

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

On Wed, 06 Oct 2004 07:42:25 -0500, Tamaroak
wrote:

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.

Now that's an interesting approach. Why do you run that?

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

On Wed, 06 Oct 2004 09:20:34 -0400, John Wentworth
wrote:

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?


Mercury recommends 25W-40 oil for Mercruiser engines, back in '89 they
rcommended straight 30 weight. In '89 Mercury sold 30 weight and warned
against multi-viscosity oils, now they recommend and sell it.

Which brings up another guestion.

On two cycle engines, the TC-W3 standard (I hope I have that right) is
the "standard" to which all engine are supposed to be built, right?

Then why do the various manufacturers all consider non-factory oil a
bad thing?

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

It's supposed to hold up better than conventional oil. Sometimes, like
last year when I went to Alaska via the Inside Passage, changing oil
every 100 hours isn't convenient. I want oil to be able to go a little
farther than that if i have to and the extra cost isn't significant,
especially after we spent $2500 for fuel.

Capt. Jeff

On Wed, 06 Oct 2004 15:34:41 -0500, Tamaroak
wrote:

It's supposed to hold up better than conventional oil. Sometimes, like
last year when I went to Alaska via the Inside Passage, changing oil
every 100 hours isn't convenient. I want oil to be able to go a little
farther than that if i have to and the extra cost isn't significant,
especially after we spent $2500 for fuel.

Interesting.

Thanks.

Later,

Tom

OMG... Here we go again.
-Dan

"WaIIy" wrote in message
...

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?

"John Wentworth" wrote in message
...

Mercury recommends 25W-40 oil for Mercruiser engines, back in '89 they
rcommended straight 30 weight. In '89 Mercury sold 30 weight and warned
against multi-viscosity oils, now they recommend and sell it.

That's a good BINGO.
-Dano

John Wentworth wrote in message ...
WaIIy wrote:

Mercury recommends 25W-40 oil for Mercruiser engines, back in '89 they
rcommended straight 30 weight. In '89 Mercury sold 30 weight and warned
against multi-viscosity oils, now they recommend and sell it.

Interesting, but I am doubtful. I installed 2 new mercruiser 5.7 liter
I/Os in year 2000. The owners manual specified their own 25w-40 with
other multivis as alternatives. It specifically recommended against
synthetic oils. That seemed weird, so I called my friend who has a
1985 mercruiser 5.7 liter I/O. His owners manual was identical in all
respects about oil except it did not say anything about synthetic oil.
Somewhere between 1985 and 2000 Mercury saw fit to add one sentence to
the manual to recommend against synthetics. Neither manual listed
straight weight as a first or second option.

"K. Smith" wrote in message
...



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.


K: Either you have just enough information to be dangerous or you badly
mis-stated what you were trying to say.

All oil, single or multigerade thin as they heat up. Multigrade oils just
don't thin out as fast.

If by "plastics" you meant "polymers" then part of what you said is correct.
A multigrade starts with a base that is comparable to the lower weight
number and adds polymers that react with heat. This reaction slows down the
thinning action, it does NOT reverse it.

What most people do not realize is that the two numbers are given from
entirely different tables. There is a range of viscosities that is covered
under the "W" range and another range of viscosity for non-W. An oil rated
at 75W has about the same viscosity as an oil rated at 10.

Another important aspect of the rating is the fact that SAE motor oil is
rated at 100 degrees C. When you need the viscosity this is the
temperature that you oil is likely to be at.

A multigrade oil allows you to have a higher viscosity oil at 100 degrees C
that you can still manage to pump out of the oil pan when the temperature
drops well below freezing. It comes at a price, however. The polymers tend
to be fragile, and can be damaged by excessive heat or contamination. A
20W-40 is a much more robust oil than a 5W-40 because it started with a
heavier oil and doesn't need as much treatment to stretch it out.

Putting additives in a multigrade oil is also taking a risk for the simple
matter that it may be impossible to tell how the additive might react with
the various polymers in the oil. I doubt that the additve manufactures
fully test against every possible brand and weight of oil, and even if they
did I doubt even more that they would let you know if they discovered a few
brands that reacted badly with their additive.

If you live in Florida then you really don't need to worry about multigrade
oils. Run 40 weight and you are fine. If you live in Bismark North Dakota
in the winter time a multigrade oil is exactly what you need.

Rod McInnis