rmcinnis wrote:
"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.

Yes & I apologise, sorry I was trying to show that a low temps multi
grade oils stayat their lower "grade", good thing you blokes are keeping
an eye on me:-)


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

Yes

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.

Yes again

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.

Yes & there is the rub with raw water cooled boat motors.

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



Thanks Rod

K

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, engine manufacturers recommend multi-grade oils for Florida as well.
engines still need pressure oil upon startup, even at 22C


Rod McInnis

rmcinnis wrote:

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.


"K. Smith" wrote in message

Yes & there is the rub with raw water cooled boat motors.



One thing to keep in mind is that inboard and stern drive engines run with
hotter oil temperatures than their automotive cousins, even though their
coolant temperatures are around 140-165 vs. 180-210. An automotive engine
normally operates at a much lower power output and rpm (2500 rpm @ 70mph)
and air flow is constantly flowing over and around the motor while running
down the road. That air from the car's volocity and/or the radiator fan
absorbs the operating heat emitted from the engine and the oil pan.

In a boat, an engine is located in a cramped area and also is sometimes
insulated to reduce sound and heat transfer to the other areas of the boat.
There is no 70mph air flow helping to cool the motor or the oil pan. A
marine engine is cruising at a much higher rpm and power output for hours at
a time. The internal parts of the engine, pistons, rods, bearings, etc. run
at a much higher temperature than the 140 degree cooling water, and the oil
has to asborb that extra heat. The combination of limited air flow and
higher power output in a confined space make the oil in a marine engine run
quite a bit hotter than in cars. You can test this out by using an infrared
temp gun on your boat and your car if they use similar engines. It is
especially true if you run the car and the boat at the same speeds for
several hours.

In a previous post, Karen was correct in a way. When a multi grade oil gets
severely overheated, the oil can thicken up depending on its additive
components. Today's mulit grade oils are much more heat tolerant than the
ones from years ago.

Bill Grannis
service manager

When a multi grade oil gets
severely overheated, the oil can thicken up depending on its additive
components.

that is also true of single weight oils, but you knew that didn't you (you
being a service manager and all)?

petro lub oils usually get pretty damned gooey at about 300F, hence one of the
advantages of syn oils, which make it usually to about 500F.

petro oil can cause exhaust valve sticking in high performance engine of long
ago designed to run on leaded fuel (which lubed the valve stems and seats) that
now try to run unleaded.

Bob wrote:
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.


In a Mercury Marine service manual I have that covers the early '80's
the recommendation is:
Lowest temp is 90°= SAE 40 "SE"
Lowest temp is 32°= SAE 30 "SE"
Lowest temp is 0°= SAE 20W "SE"

For much of the United States that equals SAE 30, oil to be changed
every 100 hours or 60 days, whichever comes first.

Also: " We recommend Mercury Marine 4-Cycle Marine Motor Oil Formula 4R.
If not available, use any good grade automotive oil of correct viscosity
which has an API classification of "SE".


One thing for sure, the topic "Oil for my boat" will produce a deluge of
responses. Can a "dead reckoning" topic be far away?

On Thu, 07 Oct 2004 09:13:28 -0400, John Wentworth
wrote:

~~ snippage ~~

One thing for sure, the topic "Oil for my boat" will produce a deluge of
responses. Can a "dead reckoning" topic be far away?

Kewl!!!!

All the best,

Tom
--------------

"What the hell's the deal with this newsgroup...
is there a computer terminal in the day room of
some looney bin somewhere?"

Bilgeman - circa 2004

On Thu, 07 Oct 2004 16:12:52 GMT, WaIIy
wrote:
OK, Bill. Thanks for the info. Now, what should I put in my 1997, 5.7L
Mercruiser I/O, given that my boating is done in the Chesapeake Bay.

John H

That was also my question. What oil for 1989 5.7 in Cleveland?

========================================

When I was running my 5.7 on Long Island Sound I would use 30 weight
for the oil change at winter lay up but for my mid-summer oil change I
would use 40 wt. Here in Florida I'm running 40 wt year round based
on the advice of my mechanic. Winter time water temps here are
comparable to summer temps in the north east. In the summer the water
is at 85 to 90 and engine cooling can be a serious issue.

"Bob" wrote in message
m...
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.

From my 1987 Mercruiser Blue Water Inboards Operation and Maintenance Manual
(260hp)

"IMPORTANT: The use of multi-viscosity oils specifically is not recommended
for use in MerCruiser Engines." Then follows a chart that recommends SAE
20, 30 or 40 depending on temperature. There is no mention of synthetics in
this manual.-Dano

I just today put Amsoil 15-40 marine diesel in that 1987 260 hp 5.7
Mercruiser as I have been doing for a couple years now. I'll know in
2500 hours whether it was a good move or not!

Capt. Jeff

guys, ask the manufacturer of the engine for the kriste's sakes, and every last
one of them flatly states multi-grade for most all but extremely unusual,
virtually unheard of conditions for a recreational engine.

btw, Mercruiser isn't a manufacturer of engines. but play silly pattycake with
each other for as long as you wish.

From: WaIIy
Date: 10/7/2004 12:12 PM Eastern Daylight Time
Message-id:

On Thu, 07 Oct 2004 09:12:24 -0400, JohnH
wrote:

On Thu, 07 Oct 2004 11:59:35 GMT, "Billgran"
wrote:

rmcinnis wrote:

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.


"K. Smith" wrote in message

Yes & there is the rub with raw water cooled boat motors.



One thing to keep in mind is that inboard and stern drive engines run with
hotter oil temperatures than their automotive cousins, even though their
coolant temperatures are around 140-165 vs. 180-210. An automotive engine
normally operates at a much lower power output and rpm (2500 rpm @ 70mph)
and air flow is constantly flowing over and around the motor while running
down the road. That air from the car's volocity and/or the radiator fan
absorbs the operating heat emitted from the engine and the oil pan.

In a boat, an engine is located in a cramped area and also is sometimes
insulated to reduce sound and heat transfer to the other areas of the boat.

There is no 70mph air flow helping to cool the motor or the oil pan. A
marine engine is cruising at a much higher rpm and power output for hours
at
a time. The internal parts of the engine, pistons, rods, bearings, etc. run

at a much higher temperature than the 140 degree cooling water, and the oil

has to asborb that extra heat. The combination of limited air flow and
higher power output in a confined space make the oil in a marine engine run

quite a bit hotter than in cars. You can test this out by using an infrared

temp gun on your boat and your car if they use similar engines. It is
especially true if you run the car and the boat at the same speeds for
several hours.

In a previous post, Karen was correct in a way. When a multi grade oil gets

severely overheated, the oil can thicken up depending on its additive
components. Today's mulit grade oils are much more heat tolerant than the
ones from years ago.

Bill Grannis
service manager




OK, Bill. Thanks for the info. Now, what should I put in my 1997, 5.7L
Mercruiser I/O, given that my boating is done in the Chesapeake Bay.

John H

That was also my question. What oil for 1989 5.7 in Cleveland?