Here copied and pasted from another website, is the best article on oil I have ever read.
Sent 11 June 2009 - 06:12 PM
Marine Oils Ain't Special
If you spend a lifetime talking to both the R&D guys and the organic chemists that support their efforts, you will get confirmation on all your suspicions. All the "factory approved" Oils must come from somewhere. Merc and Volvo don't make oil. They give various suppliers a set of performance criteria and take the low bid. They then test the oil to make sure it meets their minimum standard and then have it stuck in their bottle. With cars it's easy. The spec is not very aggressive. Honda Certified Motor oil is actually Mobil Clean 5000. The bottom of the food chain. Will it get you through the warranty? Sure. Can you do better? You bet. I don't know about you guys, but I like the fact that I just sold our Oldsmobile with 386,000 miles on it. You ain't going to get there on Mobil Clean 5000, but we did with Mobil-1.
The marine oil spec is a bit more aggressive, but the stuff still is not a blend to order product. It is a re-brand of an existing high performance motor oil. A blend to order product for that limited market would be $12/quart. oil batches are either blended in an on-line blender where a row of meters proportionally blend the correct components at the rate of around 400 gallons per minute, or they are batch blended by hand in 9,000 gallon kettles at a very high cost premium. Some specialty lubes get made that way, but they cost a fortune.
The exposure that the marine industry has now is that all the newer generation car engines are going for increased fuel economy. This means lighter engine components and tighter tolerances which allow for the use of really thin Oils. Heavy Oils create parasitic drag wasting fuel and robbing horsepower. Also, reduced windage in the crankcase results from not having as much wetted surface oil throw-off to control. As the crank runs into the oil being thrown off the bearing surfaces, a rope effect occurs that drags the rotating assembly down. Tighter tolerances and thiner Oils limit that effect. Marine engines cannot be manufactured to such tight tolerances as the higher component loads generate more thermal expansion. Build them that tight and they will seize up at operating temperature. Try to use light Oils in them and they will beat themselves to death. Problem is that more and more oil compounder's are finding it necessary to eliminate their marine friendly Oils as they are being forced to blend more flavors of the really thin specialized stuff, which is their bread and butter.
If you think Marine Oils are a "special secret formula", your wrong. Will they get you to 1,000 hours on a gasoline engine? I've yet to see it but maybe if you change it often enough. I'll see you guys on the north side of the 1,000 hour club with my Mobil-1.
RECREATIONAL MARINE Oils...
I've followed the oil controversy for some time, and read the comments with interest, but it seems that most opinions are simple statements without any technical reference. I'm not a subject matter expert by any means, but have worked with some of the top Lube Chemists and Application Engineers in the business, and hopefully will be able to remove some of the apparent mystery surrounding "Marine Spec" Oils.
First of all let's identify the fundamental differences between an automotive engine and a recreational marine application. Cars typically use a moderate percentage of their available horsepower to achieve cruising speed, then a much lower percentage to maintain said speed. A marine engine as we know is constantly loaded like a truck climbing a mountain and never reaching the top. As such, the marine engine combustion chamber temperatures are, on average, significantly higher than a comparably sized automotive engine. This alone creates a need for an extreme pressure component to be deposited on the cylinder walls to prevent compression ring and piston skirt scuffing. Marine engines are also jetted fatter on their fuel curve, and use a much colder spark plug. Control of ignition timing is also much more critical. The good news is that there is an inexhaustible supply of cooling water available to help with other related excess heat issues.
Secondly, engine Oils have a propensity to attract moisture. With the boat sitting at the marina for weeks on end, marine oil will typically have an emulsifier added to help keep the oil in suspension until the next engine heat cycle drives out the moisture. If "moist" used oil is left in the crankcase say over the winter, it is not uncommon for acids to form which attack the lead/iridium coating on the engine main and rod bearings, leading to failure during the first cold start of the next season.
Let's set these two issues aside for now, and discuss the primary mission of motor Oils. Most people think lubrication, and although lubricity is important, the primary purpose is to remove heat. To accomplish this, the oil must be in the right place at the right time and stay there until its mission is accomplished. Different Oils achieve this utilizing different approaches.
Mineral based Oils as pulled from the ground and refined have a multitude of different sized molecules. Quite simply, the medium sized ones do a pretty good job right out of the box. The big ones hang in there on a 90 degree plus day, but start to turn to tar as temperatures grow cold. As stated before, oil does no good if it's not where it's needed when it's needed. Cold start-up can be a problem with straight weight conventional Oils for the first few seconds. To help with this, blenders add a pour depressant additive to the mix which tends to free up these big fat molecules as the temperatures fall.
The small molecules do not have a low pour point issue and will flow quite well at colder temperatures; however they have a nasty habit of vaporizing out the exhaust when temperatures climb. Another additive known as a viscosity improver attaches to these guys, and helps them to thicken as the temperature goes up. This is how 20W-50 oil can act as a 20 weight in winter and a 50 weight as temperatures elevate.
Lastly, in an extreme pressure application such as the cylinder wall to piston skirt scuffing phenomena common to marine engines, a blender will utilize an extreme pressure additive to negate this exposure. These materials, typically heavy metals, will deposit themselves into the tiny scratches in the cylinders and pistons providing a barrier of dry lubricant which stays in place until the carrier oil has an opportunity to deposit a new batch during the next splash cycle. These compounds can be moly-lithium-disulfide, zinc, graphite, lead, iso-sulfinates, and iso-calsinates (sulfur or calcium).
Marine Oils and specifically the Merc oil blend that many of you defend so strongly achieves the required marine certifications in several ways. An anti-corrosion additive keeps the excess moisture at bay, while the viscosity enhancer and pour depressant make their base oil stable over a broader operating range.
Sounds like we have it all covered, but there are a few negative qualities to these additives. The heavy metals need to be use in precise quantities and need to stay in suspension in order to be effective. Too little in the mix due to poor quality control, or additive fall-out in the oil pan, and the skirts are going to get scratched. Too much, and this stuff ends up in the combustion chamber as tiny little blobs of glitter that glow at superheated temperatures causing pre-ignition like you would not believe.
The pour depressants, viscosity improvers, and moisture dispersants seem harmless enough, but they all have one thing in common. They decrease the carrier oil's base line lubricity. That's not a good thing.
I think the Merc oil is fine and if that is what makes you happy keep using it. But I think we can do better under certain circumstances. Engine builders are notorious for being slow to accept changing lubrication technology. They want oil that they can get in limited quantity in their bottle at a cheap price. It needs to get them through their warranty period, but not necessarily make their engine last forever. It's only when their customers insist on a better mouse trap are they forced to provide one. A case in point is Honda factory approved 5w-20 premium motor oil. Available at their dealer network, this stuff is actually Mobil Clean 5000. That’s the bottom of the food chain at Mobil. Will it go 5,000 miles in your new Acura and get you to the end of the warranty period. You bet. Can you do better for your new ride? You bet.
So what about Synthetics? Remember the molecule size discussion earlier? Mobil-1 is made from PAO ester base oil manufactured by Mobil Chemical. They take a base fluid and through catalyst technology are able to re-arrange things at the molecular level ending up with a base oil with nothing but the medium sized molecules we are looking for, which is stable over the complete operating temperature range. Straight out of the tank, it can out perform the best conventional Oils, without the need for additives. Mobil has developed special additive packages to enhance these formulations even further to the point where these Oils can do things never thought possible.
I've used these Oils in our fleet of recreational boaters since they came out. High Performance and Heavy Cruisers alike, I've seen overheating due to raw water pump failure where the exhaust bellows have burned off, and the head gaskets have failed, but the cylinder walls, valve guides, and main and rod bearings were undamaged. I have actually seen a piston from Kyle Petty's NASCAR engine that drove back to the pits in Daytona after an accident, without water in the block. The top of the piston was melted, but the cylinder wall was unharmed.
Why Mobil-1 is not marine certified? Well because it's a small volume sale that requires an upfront expenditure. Also, I would not let dirty Mobil-1 sit in my engine during winter lay-up as it is not loaded up with moisture dispersant. What about viscosity enhancers, pour depressants, and extreme pressure additives? Doesn't need them and as stated before they tend to reduce lubricity. Ain't broke, don't fix it.
I see mileage and WOT increases in every case after switching to 15W-50 Mobil-1 in recreational marine applications. I drop it at 100 hours or at season's end. Fill her with fresh and wait for summer. Your choice, but I hope this helps with the decision making process.
SYNTHETIC Oils...
I had posted comments relative to recreational marine Oils, and have had several inquires asking if this or that oil is a good choice. My answer is "your guess is as good as mine". I use Mobil-1 for the reasons I stated. I would however like to attempt to clarify the term "Synthetic" as applied to today's Oils as marketed.
PAO esters were developed to replace mineral base Oils which have been in use since the introduction of the internal combustion engine. Mineral oil's suitability for blending into lubricating oil base stocks depends on the crude source and refining process utilized. Keytone solvent base refining and clay filtration was utilized to remove the wax and other impurities from crude lube extracts for years, with the wax being sold as a consumer product. Nowadays, a hydrogen based process or hydro-treating is combined with different catalysts to produce a mineral base oil of high quality. A rating system was developed using a term known as "base number" whereas the higher number the better. These high base number blending stocks require fewer additives in order to produce a suitable consumer end product.
PAO esters are still today, the holy grail of base stocks as they out perform any mineral oil based compound by a long shot. Because these PAO fluids are proprietary, are extremely expensive to produce and are backed up with limited production capability, the remainder of the industry was scrambling back in the early 1990's for a cheaper alternative in order to enter the lucrative synthetic market. Enter the "severely hydro-treated" mineral base Oils.
Refiners began to market these high base number mineral Oils as "Synthetic" The PAO contingent sued as they felt that identifying these severely hydro treated base Oils as a pure synthetic was out right fraud. As there were no government standards at that time for synthetic Oils, the courts claimed that no one could actually claim what constituted a synthetic, and what was not. I feel that this was a true disservice to the consumer, as now the market is flooded with "synthetic Oils" and we as consumers do not know which are true PAO esters and which are high base number want-a-bee's.
My feeling is this. Unless you have documented performance records over a long period of time for yours or a similar application, don't experiment. The trouble is that when we arrive at the parts store, all the bottles look alike. For example, I will always use Mobil-1 15w-50 extended performance in my 496 Mag-HO as I truly feel that it's the best I can get, and much better than it actually has to be. On the other hand, I would not put Quaker State , Royal Purple, or several others in my lawn mower due to my own personal experience. If you are not experienced, stick with the Merc oil or the Volvo oil. If you are set on an alternative, compare it's specification to the Mobil-1 data below. If your supplier refuses to provide the data, keep looking.
Mobil-1 15w-50…
API Certifications SF,SG,SH,CD
General Motors 6048-M, 6049-M, 6085-M,
Ford M2C153E
Total Base Number 12
Sulfated Ash 1.3
HT/HS, cP @150 C
Low Temp Viscosity 3500 @ -15 (Cranking cP)
30,000@-20 (Pumping cP)
High Temperature Viscosity 5.6 cSt at 100C
API Gravity 30.2
Pour Point -55 F
Flash Point 470 F
SUS @ 100 F 556
SUS @ 210 F 90
V.I. 170
Lastly, I see some of you are using truck fleet type Oils like Rotella-T and Mobil Delvac. Remember that these are diesel fleet Oils which are a little high on zinc additives. Diesels love Zinc. Gasoline engines do not. A high speed marine engine will get some of these heavy metal particles into the combustion chambers, which are excessively hot in a boat application. This can cause pre-ignition in a gasoline application. Remember that this effect is how a diesel engine operates, and is also how a gas engine can beat itself to pieces.
OUT DRIVE oil...
I was asked to take a minute to comment on oil usage in both the Alpha's and Bravo drives as it seems to be a topic that surfaces on the forum almost weekly. My contentions based on 30 years in the Lubes business and over 40 years in boating are as follows.
First of all, I feel that any actual consumption of oil by a drive system indicates a leak. If the drive shaft bellows accumulates gear oil, the input shaft seal is leaking and needs to be changed along with a careful inspection of the top bevel gear bearing set. If the owner is very aggressive about greasing the gimbal bearing, then it would be normal to see a small amount of carrier oil separation from the grease accumulate in the bellows, but it would not be the same color as the gear oil.
Secondly, the remaining three drive seals are all below the water line during operation and a leak would be evident by an oil sheen in the water both during operation and at rest. For obvious reasons, these also need to be fixed in a hurry due to pollution issues and also their ability to draw water into the drive housing during cool down. Other than that, there are a few gaskets and an o-ring which I have never seen fail unless they were installed improperly.
This leads us to the question of "why does my drive use oil, and where does it go?" Based on my experience I suggest the following.
Gear oil is a complex hydrocarbon matrix comprised of large chain molecules which are subject to a phenomena known as shear. Think of a gallon bucket full of tennis balls. You can only get so many balls in the bucket due to the amount of air that is surrounding each ball. Under heavy loads like water sports as you suggested, some of these molecules break down into smaller pieces due to shear. Now the bucked seems to be only 7/8 full as the tennis balls are now smaller in size, but there are more in number and if we were to weigh the bucket we would find that it weighs the same as before. We did not loose any balls, that just take up less space then they did before. The same thing happens with gear oil. As the molecules shear, they take up less space and it appears that there has been an external loss of oil. Actually it is still there, just degraded in quality somewhat. After 50 to 100 hours of this abuse, it begins to loose its effectiveness and is in need of a change out.
Gear Oils have a very high density, and a fairy low gravity. Drop a golf ball in a bucket of gear oil and it take a while to reach the bottom. Drop the same ball in Gasoline and it sinks quickly. Now weigh each bucket and you will find that the gasoline is much heavier then the gear oil. Gasoline has a higher gravity, but lower density. That’s because its individual molecules are very small with little space for air between them. The same volume of gear oil has a lesser mass as the complex chain molecules are large by comparison and have a great deal of air between them. Beat those big molecules into little ones in a high speed, non-hypoid gear case such as an out drive, and pretty soon the same amount of oil takes up less space, and needs a top off. Nothing actually leaked out, the balls just got smaller.
Lastly I'd like to suggest a variation in the method in which you and others change your drive oil. I keep reading about the air that gets trapped during refill and the subsequent need for topping off, and also about drive oil reservoir level alarms after servicing, and I can tell you I have a quick and easy solution. DON'T REMOVE THE TOP VENT PLUG. When draining the drive, remove the cap from the remote reservoir, and remove the bottom drain plug. It's important to drain the reservoir anyway as sediment accumulate in the bottom of the bottle due to thermal capillary circulation during normal operation. Get this old oil out with the rest of the drive oil as it is just as old and just as worn out. Attach your filler to the bottom drain as normal, and pump up the drive until oil appears in the remote reservoir. Look Mom, no air. The oil tube that runs up to the plastic bottle on the Gen II's exits the drive higher then the top vent plug, thus displacing the mystery air bubble. Using this methodology, I have never had to top off a drive after servicing. If you beat up an Alpha, expect to add a little oil due to shear, but if you are doing that often and there is no external leakage, the drive oil is shot and you need to think about changing it more often anyway. I use a pressure tank to fill my Bravo III-X as it take over three quarts. I change it ever 50 hours, and have never had to top a drive off because I don't give the oil a chance to begin to shear and I don't start out with an air bubble in the first place. Keep the top plug in and watch out for shear loss and I think your drive will be around for another decade or so. I hate to hear our forum members talking about top off on drives without level alarms. If you have to add a half a quart to a Bravo, or even less to an Alpha, then the top bevel gear set and bearings in the upper gear case are already taking a big hit. Hope this helps. If you ever have any oil questions, I know who to call for answers as I still keep in touch with the boys at ExxonMobil.
Re: Engine Oil Weight
