Probably because, while synthetic oil like Mobile One was around in
1986, not many people were using it so there was no need to warn against
it. By 2000, synthetics became very popular and for some reason, they
don't want you to use them.
The reason is probably because they have no control over what synthetic
you use, and they are all different.

Are there SAE or equivalent standards for synthetics as there are
regular oils?

With dino oil, they are all very
similar and the only main difference (other than things like sulfur
content) is the additives.

In other words, all good dino oils meet the various industry
standards.

So they can do testing with a high quality
dino oil and be reasonably assured that the results are reproducable
with other high quality dino oils. But with synthetics, the base
formulas and properties can be very different. Just look at the
evolution of Mobile One and you'll see that it's formula changed
drastically several times from when it was introduced in 1973; 1992,
1996, 1999, and 2002.

I wonder why the formula changed "drastically" so many times? Were
there problems?

Others have mentioned how well synthetics work in their cars; but it
seems to me that comparison is flawed. My automotive 350, at 60 mph
and 20 mpg, burns three whole gallons per hour. My twin boat 350s, at
similar rpms are each burning twelve gph. The flame front/peak
pressures/wall temp inside each cylinder is much different than any
car engine. It isn't automatic that what works at 3 gph will still do
a good job at 12 gph (at WOT it is 22 gph per engine.)

www.mobil1.com/why/synth/history.jsp

Steve

On 2 Sep 2003 20:58:43 -0700, (Bob) wrote:

Probably because, while synthetic oil like Mobile One was around in
1986, not many people were using it so there was no need to warn against
it. By 2000, synthetics became very popular and for some reason, they
don't want you to use them.
The reason is probably because they have no control over what synthetic
you use, and they are all different.

Are there SAE or equivalent standards for synthetics as there are
regular oils?

Yes, the same ones. But meeting the standards doesn't tell an engine
manufacturer all it needs to know about how their engines will perform
with a particular oil. For instance, in the synthetics vs. the natural
oils decision, they all meet the same standards. But they definitely
don't perform the same in ways that the standards testing doesn't
measure.

With dino oil, they are all very
similar and the only main difference (other than things like sulfur
content) is the additives.

In other words, all good dino oils meet the various industry
standards.

Yup.

So they can do testing with a high quality
dino oil and be reasonably assured that the results are reproducable
with other high quality dino oils. But with synthetics, the base
formulas and properties can be very different. Just look at the
evolution of Mobile One and you'll see that it's formula changed
drastically several times from when it was introduced in 1973; 1992,
1996, 1999, and 2002.

I wonder why the formula changed "drastically" so many times? Were
there problems?

I'm sure the company would call them "improvements." Just like anything
else, more R&D leads to changes in the product. However, when you
change the product with synthetics, you are changing the base
constituents that make up the oil. When you change the product with
natural oils, you're mainly changing just the additive package. The
base oil hasn't changed much in a very long time.

Others have mentioned how well synthetics work in their cars; but it
seems to me that comparison is flawed. My automotive 350, at 60 mph
and 20 mpg, burns three whole gallons per hour. My twin boat 350s, at
similar rpms are each burning twelve gph. The flame front/peak
pressures/wall temp inside each cylinder is much different than any
car engine. It isn't automatic that what works at 3 gph will still do
a good job at 12 gph (at WOT it is 22 gph per engine.)

That's probably why the manufacturers would rather you stick with what
they know works. Even if something else might work better, to them it's
an unknown until they test it.

Steve

I've been using Mobile 1 in my 5.7 Mercruiser since I bought it with 211
hours on it. I use the green top 10-30W variety which is supposed to be
for older motors. I believe part of the reason Merc doesn't want you to
use it is because they don't sell it. Their pitch is similar to other
fluids for their equipment.

I change every 100 hours (three times this year, I'm happy to say!) and
use a WIX/Napa gold filter. Ask me in 3000 hours whether I was glad to
have used synthetic....

Jeff

Jeff,

If you get 3000 hours on your 5.7 Merc without a rebuild it will be extra
ordinary. Because boat engines are typically run at a much higher percentage
of max power than car engines, they typically need rebuilding as early as 600
hours.

I have a business partner who is a long time Merc mechanic, and former boat
dealer. When I bought my power boat new in 1997, he warned me that 600-800 hours
was what I could expect based on his experience. Right now, I'm still under
200 hours TT, so don't know yet if he's right.

Obviously there are a lot of variables that affect engine longevity including
the two biggies: Not running full throttle all the time, and properly winterizing.

YMMV,

Don W.


Messing In Boats wrote:

I've been using Mobile 1 in my 5.7 Mercruiser since I bought it with 211
hours on it. I use the green top 10-30W variety which is supposed to be
for older motors. I believe part of the reason Merc doesn't want you to
use it is because they don't sell it. Their pitch is similar to other
fluids for their equipment.

I change every 100 hours (three times this year, I'm happy to say!) and
use a WIX/Napa gold filter. Ask me in 3000 hours whether I was glad to
have used synthetic....

Jeff

That's why I stuck out my timetable so far; I figure I will have this
and a lot of other things figured out by then and will know what I
should have done.

I am hoping for 2000 hours though. I change every 100 hours and run the
boat at hull speed, about 1800 rpm, which I believe to be a lot kinder
to it than up on plane at 36-3900 as it was designed for.

What does your buddy say about synthetics?

Jeff

Jeff,

I haven't specifically talked with him about synthetics, but there was a
post a while back from a guy who had used synthetic oil in his 5.7L Merc
and had some kind of premature failure. The subject was " Mercruiser Motor
Failures" from Feb 2003. You might want to search for it on Google and read
his post.

Also, if Mercury specifically doesn't recommend something I'd think it is likely
because they've seen some problems, and not because they just haven't tested
it.

YMMV,

Don W.



Messing In Boats wrote:

That's why I stuck out my timetable so far; I figure I will have this
and a lot of other things figured out by then and will know what I
should have done.

I am hoping for 2000 hours though. I change every 100 hours and run the
boat at hull speed, about 1800 rpm, which I believe to be a lot kinder
to it than up on plane at 36-3900 as it was designed for.

What does your buddy say about synthetics?

Jeff