Can I use Mobil 1 5W-50 SuperSync oil (100% synthyhetic) in Mercruiser GM
V-8 350CID (5.7 L) in 15 year old marine engine? The manual specifies
detergent 20W-40 or 20W-50 oils. What effect could have the 5W-50 viscosity
range (5W vis 20W)? The vessel is not used often, is stored on hard stand,
the winter temperatures are hardly below 10 degrees C and the engine is run
at least once every month for about 10-15 minutes.

Appeciate your thoughts
Mark Zak

Mark,

I love synthetic oil, and have been using it for years, but one of the
problems with it has to do with switching over to it on high hour, or
milage, engines. Synthetic oil has the tendency to strip away gunk
deposits within the engine. You will note that the oil looks like hell
when you change it for the first few times, that's the gunk being
removed. Now on a fresh engine it's not a problem, but on an older
engine it often results in the engine leaking oil around the seals and
gaskets, you start using oil. And this does happen, I've seen it.

The other issue, and it's not as big, marine oil has more rust
inhibiters in it because of the wet enviornment marine engines operate
in. So you can get some rust inside the block if you use synthetic. But
I will say that the last marine engine that I tore down had been run
with synthetic oil since after break in, and it had no signs of rust
inside, so I'm skeptical of the rust argument.

The 5 weight oil may be too low, you could get some knocking at start
up if you don't have lots of oil pressure (a good rule of thumb is a
350 needs a minimum of 10 pounds of pressure for every 1000 RPM's), not
a good thing. I would go with a minimum of a 20 weight oil.

John

"Capt John" wrote in message
ups.com...
Mark,

I love synthetic oil, and have been using it for years, but one of the
problems with it has to do with switching over to it on high hour, or
milage, engines. Synthetic oil has the tendency to strip away gunk
deposits within the engine. You will note that the oil looks like hell
when you change it for the first few times, that's the gunk being
removed. Now on a fresh engine it's not a problem, but on an older
engine it often results in the engine leaking oil around the seals and
gaskets, you start using oil. And this does happen, I've seen it.

Actually, it's much more likely that the older engine already has leaking
seals or gaskets before you start using the synth oil. In a sense, it would
be a good thing that it would show you the leak. In any case, the leaks are
very minor. I would much rather know there's a problem than have it masked
by something.

The other issue, and it's not as big, marine oil has more rust
inhibiters in it because of the wet enviornment marine engines operate
in. So you can get some rust inside the block if you use synthetic. But
I will say that the last marine engine that I tore down had been run
with synthetic oil since after break in, and it had no signs of rust
inside, so I'm skeptical of the rust argument.

The 5 weight oil may be too low, you could get some knocking at start
up if you don't have lots of oil pressure (a good rule of thumb is a
350 needs a minimum of 10 pounds of pressure for every 1000 RPM's), not
a good thing. I would go with a minimum of a 20 weight oil.

I have no data about this, so I'll take it as accurate.

"Mark Zak" wrote in
:

Can I use Mobil 1 5W-50 SuperSync oil (100% synthyhetic) in Mercruiser
GM V-8 350CID (5.7 L) in 15 year old marine engine?

Wow! At $3-5 a quart, the ol' GM 350 oughta damn near last
forever!....yeah, right.

The manual
specifies detergent 20W-40 or 20W-50 oils. What effect could have the
5W-50 viscosity range (5W vis 20W)?

Too thin when it's cold? 5 weight oil is like a sewing machine oil.
Wonder how well it keeps those cold rings away from those fragile, cheap GM
cylinder walls?? 20 weight is more than thin enough. We're being
conditioned so "they" can make $$$AU

The vessel is not used often, is
stored on hard stand, the winter temperatures are hardly below 10
degrees C and the engine is run at least once every month for about
10-15 minutes.

Hmm...I'd dump it if I didn't use it before it becomes worthless from the
awful boat depreciation. Oil pales in comparison to what its book value
drops.

I'm unfamiliar with Australian oil ratings as I'm on the other side of the
planet. Here, what concerns me is our oil (both dino and home made) has
been quietly devalued because it cannot pass the new SAE tests for 2-stroke
and 4-stroke diesels, once these were separated tests. So, you look on the
fancy can with the checkered flags and pictures of NASCAR race drivers and
in the SAE rating circle it says SJ or SK or whatever S rating the gas
engine manufacturers are using now....but NOT D-2 or D-4 for diesel use.
What have they left out? Diesel oils all have detergent in them because of
all the nasty carbon blowby that turns them black. Have they quietly
stopped adding detergent to keep the engines (gas and diesels) clean? Who
made that stupid decision....car manufacturers trying to wear out the cars?

I'm not fascinated with home made oils. I used Mobil 1 synthetic oil in my
Honda EU3000i electronic power plant a couple of times when it was new.
Synthetic oil was rated for air-cooled engines, not water cooled cars. It
was EXPENSIVE. I didn't care, it doesn't use much. When I sucked the
synthetic oil out and looked at it after 100 hours, I was scared I'd ruined
the Honda. It looked like it was BURNED!...it was BROWN! That ended that.
I started using the same Rotella-T (Shell) or Chevron's Velo 400 4-stroke-
rated DIESEL oils that American Truckers driving like hell down the
interstate with amazingly heavy loads on their engines run for millions of
miles between overhauls. What professional trucking companies use to
maximize their engine life speaks VOLUMES more as to what is the right oil
to use in any engine.....than the marketing department's motive of any oil
company trying to squeeze $5/quart out of some home made oil in the
checkered flag can. The genset seems ok at a thousand hours and Velo or
Rotella DON'T come out BROWN!...(c;

Larry W4CSC wrote:

I'm unfamiliar with Australian oil ratings as I'm on the other side of the
planet. Here, what concerns me is our oil (both dino and home made) has
been quietly devalued because it cannot pass the new SAE tests for 2-stroke
and 4-stroke diesels, once these were separated tests. So, you look on the
fancy can with the checkered flags and pictures of NASCAR race drivers and
in the SAE rating circle it says SJ or SK or whatever S rating the gas
engine manufacturers are using now....but NOT D-2 or D-4 for diesel use.
What have they left out? Diesel oils all have detergent in them because of
all the nasty carbon blowby that turns them black. Have they quietly
stopped adding detergent to keep the engines (gas and diesels) clean? Who
made that stupid decision....car manufacturers trying to wear out the cars?

I'm not fascinated with home made oils. I used Mobil 1 synthetic oil in my
Honda EU3000i electronic power plant a couple of times when it was new.
Synthetic oil was rated for air-cooled engines, not water cooled cars. It
was EXPENSIVE. I didn't care, it doesn't use much. When I sucked the
synthetic oil out and looked at it after 100 hours, I was scared I'd ruined
the Honda. It looked like it was BURNED!...it was BROWN! That ended that.
I started using the same Rotella-T (Shell) or Chevron's Velo 400 4-stroke-
rated DIESEL oils that American Truckers driving like hell down the
interstate with amazingly heavy loads on their engines run for millions of
miles between overhauls. What professional trucking companies use to
maximize their engine life speaks VOLUMES more as to what is the right oil
to use in any engine.....than the marketing department's motive of any oil
company trying to squeeze $5/quart out of some home made oil in the
checkered flag can. The genset seems ok at a thousand hours and Velo or
Rotella DON'T come out BROWN!...(c;


Larry,

Thats an interesting insight. I grew up on a farm where we ran diesel
tractors, and we used to buy diesel rated oil from the local CooP (pronounced
Co-OP for you city slickers by the 50 gal drum. Later, I owned a Cummins
powered diesel truck, and always used Rotella because thats what the owners
manual recommended.

I've always run regular 10W-30 motor oil in my gas powered vehicles, and have
generally had good luck with it, but I'll bet that you are right about the
diesel rated oils being higher quality and having better detergents. Diesels
generally run compressions of 24:1 where the average auto today is more like
8:1. There is a lot more pressure on the rod and main bearings in a diesel
because of the higher compression.

I'll bet that there are some mechanical engineers lurking about who could
probably explain all about the SAE oil ratings in great detail.

Don W.

Don W wrote in
:

There is a lot more pressure on the rod and main bearings in a diesel
because of the higher compression.


The new C-2 and C-4 ratings for 2 and 4 stroke diesels have to do with what
type of detergent is put in the oil to keep the carbon blowby from
destroying it. The detergents in the old gas oils couldn't pass the tests,
so SAE forced them to remove the old CD or CE, etc., ratings from the super
cans with the checkered flags on them. Car oil has an S rating only if you
take a look at it, now. NEVER use these oils in ANY diesel engine.....

Reminds me of Wolf's Head....(c;

Just a few points, the Chevy 350 is probably one of the best engines
ever built. These engines last many years in marine applications. Their
are very few other gas engines that you can say the same thing about.
They were easy to get parts for, and even heavy duty parts were cheap,
they were simple to build or repair. They weren't perfect, but they
were very reliable, and took a beating.

Diesel oils are made to handle sulfur which is a main concern when it
comes to blow by, they are also formulated to keep contaminates in
suspension, so it comes out with the oil when you change it. That dirt
in the oil is not dirt left in the engine. When you switched your
little Honda over to synthetic you saw what you should expect to see,
dirt in suspension being removed from the engine. Synthetic oil holds
contaminates in suspension better than standard oil, after a few
changes the engine starts to clean itself out, and the oil looks better
when you drain it. By the way, diesel manufacturers are testing their
engines with synthetic oils. I'm sure they'll work just fine, the
problem will be cost, with synthetic their probably looking at about
$50 to $100 worth of synthetic vs $15 to $30 or so of standard oil.

When you talk about overhauls on trucks, they don't run the engines
until they die, and overhaul them. They run them to some point, pull
the engine, and overhaul it, or install another one that has been
overhauled and overhaul the one they just pulled. Their in the business
of hauling freight on time, waiting for a breakdown in the middle of
nowhere doesn't work for them.

Gen sets and long haul engines last a long time because their running
most of the time at constant speeds and loads, it's the start and stop
kind of operation that kills the engine.

And Rotella, Velo and Delo all come out as black as night from a
diesel, even on new engines.

On Fri, 27 May 2005 14:40:34 GMT, "Mark Zak"
wrote:

Can I use Mobil 1 5W-50 SuperSync oil (100% synthyhetic) in Mercruiser GM
V-8 350CID (5.7 L) in 15 year old marine engine? The manual specifies
detergent 20W-40 or 20W-50 oils. What effect could have the 5W-50 viscosity
range (5W vis 20W)? The vessel is not used often, is stored on hard stand,
the winter temperatures are hardly below 10 degrees C and the engine is run
at least once every month for about 10-15 minutes.

Appeciate your thoughts
Mark Zak


Synthetic can be searching on older engines, so watch the oil filter
for a while, and look out for case leaks

Brian Whatcott Altus, OK

Gentlemen,

I appreciate and thank you for your responses, most informative and I have
learned a lot.
Once again, many thanks and regards
Mark Zak


"Mark Zak" wrote in message
...
Can I use Mobil 1 5W-50 SuperSync oil (100% synthyhetic) in Mercruiser GM
V-8 350CID (5.7 L) in 15 year old marine engine? The manual specifies
detergent 20W-40 or 20W-50 oils. What effect could have the 5W-50
viscosity range (5W vis 20W)? The vessel is not used often, is stored on
hard stand, the winter temperatures are hardly below 10 degrees C and the
engine is run at least once every month for about 10-15 minutes.

Appeciate your thoughts
Mark Zak