Why no synthetic oil for marine engines?

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Originally Posted By: Jdblya
Originally Posted By: PT1
The Amsoil ASD 30w is the only synthetic I would consider as it is also a proven performer.


I looked it up, it is actually ACD and it does look pretty good also.


Opps...my bad.
 
Originally Posted By: RTexasF
Mercruiser's 25W40 is a synthetic blend and today's (10 years old or so) Volvo engines come with Volvo synth in them right from the manufacturer. The Volvo branded oil that dealers use is also synthetic if it's in a 50 gallon drum or a quart container. It is required for warranty.


The Merc Quicksilver comes in both dino or syn blend. West Marine carries both. $19.99/gal for dino $23.99/gal for the syn blend.
 
My daughter and son in law have a 34 ft. Sea Ray, twin 500 ci engines and their dealer told them to use M1 oils. not sure of the wt.
 
Originally Posted By: PT1
Originally Posted By: RTexasF
Mercruiser's 25W40 is a synthetic blend and today's (10 years old or so) Volvo engines come with Volvo synth in them right from the manufacturer. The Volvo branded oil that dealers use is also synthetic if it's in a 50 gallon drum or a quart container. It is required for warranty.


The Merc Quicksilver comes in both dino or syn blend. West Marine carries both. $19.99/gal for dino $23.99/gal for the syn blend.


Back when I bought my 40HP 4-stroke in 2002 you could get the regular Mercury 4-stroke oil( conventional = black bottle )in 25W-40. Doesn't look like they still offer it however. Looks like it is blend only??? I used to run the 25W-40 in summer then swap to the 10W-30 for winter( waterfowl hunting Oct-Feb ).

I don't use the boat as much in the summer anymore so I have gone to 10W-30 changed once a year. I could get dino 25W-40 at one point though. Marina didn't always have it in stock though so I was always sure to call ahead far enough that they could get some for me.
 
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Mercruiser still shows both 25W40 dino and 25W40 syn blend on their website so both are still around and available.
 
Merc has shyed away from synthetics for reasons of storage.

"synthetic" is used to market such a wide range of oil basestocks and blends that they have no guarantee the end user might pick one that doesn't store well.
 
Originally Posted By: wileyE
Merc has shyed away from synthetics for reasons of storage.

"synthetic" is used to market such a wide range of oil basestocks and blends that they have no guarantee the end user might pick one that doesn't store well.


Good point. Also one needs to consider water contamination of oil. Some Gr V oils are esters that are hygroscopic and miscible with water.
 
I was looking around the Tohatsu site and came across this statement in their FAQ:

Because outboard motors have raw water cooling systems and run in varying water temperatures, unlike other water cooled 4-stroke engines, it can be difficult to maintain sufficient engine temperature in some geographic areas. Therefore, we do not always recommend using synthetic oil in our 4-stroke outboard motors, especially during break-in, due to the lowered engine temperature which could contribute to fuel/oil dilution.

Are they saying that synthetic will allow the engine to run that much cooler or are they figuring people will run the synthetic longer?

I don't quite believe the former and fully agree that in any type of marine engine frequent oil changes are the best policy.

Ed
 
Ed,

No. What they're trying to say, without filling in the details, is that a synthetic is not always the best choice where higher fuel and water dilution exists, for the reasons stated earlier in this thread.

It's a CHEMISTRY issue. The chemistry of some synthetics is not as tolerant when dumping lots of fuel and water into them. The simpler composition of a conventional is an advantage under these conditions.
 
Originally Posted By: friendly_jacek
Originally Posted By: wileyE
Merc has shyed away from synthetics for reasons of storage.

"synthetic" is used to market such a wide range of oil basestocks and blends that they have no guarantee the end user might pick one that doesn't store well.


Good point. Also one needs to consider water contamination of oil. Some Gr V oils are esters that are hygroscopic and miscible with water.


Why would a marine engine injest water into the engine any more than a car engine? So far I see no reason not to use synt oil in marine use.
 
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I see why one may run richer due to the temperature, however, especially on say a fuel injected inboard, wouldn't they design the fuel management to not run so rich?
 
Originally Posted By: tig1
Why would a marine engine injest water into the engine any more than a car engine? So far I see no reason not to use synt oil in marine use.


Have you ever stood in a bilge? Have you ever been underway on the water? Do you know what raw water cooling is all about?

I'm not trying to be crass. But once you've had boats for a while, the reasons are beyond obvious.
 
Originally Posted By: Pablo
tig1 - I agree. There are some "interesting" comments in this thread. Especially with well compounded synthetic marine oils not tolerating fuel and water.......


Pabs, I guess I'll be blunt. Have you ever owned a boat? How much personal experience do you have with marine engines?
 
I live on the Puget Sound. Yes. A lot. I don't dispute the wetness issue. I do dispute a couple things though. While a marine engine is more prone to ingest water vapor, there is no reason why the engine (other than [censored] poor design, maintenance or mechanics) that the engine should injest liquid water.

I'll be blunt. What you say about synthetics not being tolerant of water and fuel is wrong. In reality it's the opposite. Synthetic oil, especially synthetic marine oils are actually better with raw water cooling systems and high fuel/oil loads. It's a chemistry issue. They are less prone to shear, they have higher natural VI's and premium oils have way better anti-corrosion additive packages.
 
Originally Posted By: Volvohead
Originally Posted By: tig1
Why would a marine engine injest water into the engine any more than a car engine? So far I see no reason not to use synt oil in marine use.


Have you ever stood in a bilge? Have you ever been underway on the water? Do you know what raw water cooling is all about?

I'm not trying to be crass. But once you've had boats for a while, the reasons are beyond obvious.


If your boat is sinking I guess dino would be cheaper.
 
Originally Posted By: Volvohead
Originally Posted By: tig1
Why would a marine engine injest water into the engine any more than a car engine? So far I see no reason not to use synt oil in marine use.


Have you ever stood in a bilge? Have you ever been underway on the water? Do you know what raw water cooling is all about?

I'm not trying to be crass. But once you've had boats for a while, the reasons are beyond obvious.


My bilge is usually pretty [censored] dry unless there is a ton of in and out of the water by people. My engine has raw water cooling, and as far as I know other than allowing the engine to get really hot, I don't see any water getting anywhere unless it is pulling back through the wet exhaust? I'm not trying to argue, I am trying to become more educated. I know that people sometimes have problems with wet exhaust when they have to much cam overlap and so fourth.
 
Originally Posted By: Pablo
I live on the Puget Sound.




way way off subject, but I was watching Monsterquest the other night (couldn't sleep) and they were showing Giant Octopus in Puget Sound. Pretty cool
 
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