Gasoline & Oils  Pertaining to 2 Cycle Outboard Motors

Gasoline shelf life:    According to Chevron....  "Gasoline stored in a tightly closed container in a cool place will stay good for at least a year.  It is better if the container or gas tank is almost (95%) full.  If the container or gas tank will be in the direct sun or will be heated above 80 degrees F. much of the time, add an aftermarket fuel stabilizer to the gas when you first buy it.  Gasoline-oil blends for two-stroke cycle engines stored under the proper conditions will keep as well as gasoline itself."

The oil additive therefore does not make any difference in storage life.

And this from Shell.... "All gasoline has finite storage life.  If storing gasoline longer than 6 months, you may want to use a supplement fuel preservative additive.

If aged long enough, gasoline can form gum & varnish that can cause engine operating problems, & sometimes to the engine & fuel tank.  All Shell gasoline - conventional & reformulated - meet ASTM requirements for stability (a measure of protection against oxidation that can degrade gasoline properties).  How long gasoline can be stored, depends mostly on storage conditions.  Increased temperature, exposure to air and contaminates, and the material the storage container is made of can shorten storage life.  Generally, gasoline stored for longer than 6 months will likely benefit from adding a supplemental stabilizing additive.  Usually available at your Shell service station.  Stored gasoline only in an approved container, well away from sources of ignition."

For tanks that are mostly full & going to be left for a considerable length of time, add a fuel stabilizer.  Premix a couple of gallons of gas with enough stabilizer for the total amount in the tank, then add this mixture into the tank.  Different stabilizers give different "life" times, so therefore some brands of stabilizers "do" more.

Now for my opinion on this BS.  The above oil companies are just like politicians, they say a lot but, are only trying to cover their behinds.  From my observations, I think that the newer non-leaded fuels produced by modern technology aren't anywhere near prone to "varnish" as the older leaded gasoline was.  My thought is that it would take serious neglect and long, long periods of storage to form "varnish" in a current fuel system.  I suspect that long term storage in a steel fuel tank would be more detrimental because of possible rusting of the steel tank, which may plug the fuel filter or get by it & into the carburetor.

How many of you just park your lawn mower after the mowing season, & it will start the next year with only a few pulls of the rope.

In the years not so far in the past, most gasoline was leaded 85 octane.  For those of you who may not know, lead is not a normal product found in petroleum, but was added into the gasoline for the purpose of lubricating the valve stems of 4 stroke automobile engines.  The automotive industry had not developed steel yet that would not gall in a high temperature situation where the valves operate in a engine.  This lead additive in the gasoline lubricated the valve stems, accomplishing this needed result.  It is not really known as to whether that this lead additive is what caused the varnish in gas tanks & carburetors if let set for a period of time, but since the non-leaded gasoline has became the norm, the varnish has about vanished from the scene.

The final end result is that all gasoline medium grade now being sold is non-leaded 87 octane & it is hard to find the older lower 85 octane.  Most outboard motor manufacturers now recommend a 87 octane gasoline. 

Also at this same early years, the oil mix was standard 30W SAE automotive oil.   A lot of improvements have been made.

Fuel to Oil Mix Ratio :  The reason for mixing oil into the gasoline is that since these engines are 2 cycle, (sometimes called 2 stroke) there needs to be oil mixed into the gas to lubricate the internal parts (piston, crankshaft & bearings) of the engine, as there is no crankcase oil reservoir or oil pump as in the 4 stoke engines.

From 1985 to 1989, Johnson & Evinrude (OMC) recommended a 100 to 1 mix, this was printed on a decal placed on motors of these years.  The actual change back to the 50 to1 mixture was made sometime in 1989.  There was a Technical Bulletin  #2162 dated March 1986, directing the mechanics to remove the decal,  replace it with a new 50/1 decal & inform the owner, when the motor was serviced in an OMC repair shop.  This was recommended for rental, commercial & heavy duty service engines.  The suspicion apparently was that some motors, under the right (or wrong) conditions, if ran at a high RPM or under a load for extended periods of time, may seize due to lack of adequate internal lubrication.

The fuel/oil mix recommended by the outboard manufacturers since about 1960 is listed at 50:1.  This means 50 parts of unleaded 87 octane gas to 1 part of TC-W2 or TC-W3 outboard motor oil.  You probably will not see much of the older TC-W2 oil out there anymore since about 1996 or so.   A marine mechanic once told me that all TC-W2 oils were regular petroleum oils while the TC-W3 were synthetic oils.   I have done some research & find that apparently the oil industry & needs have now gone beyond the specifications for TC-W3.   Some oil manufactures do make a synthetic blend or even pure synthetic oil, & since there is not a higher category NMMA in existence, the oil companies list that it meets or exceeds the TC-W3 specifications as there is nothing specified in the industry yet to designate synthetic oils. 

The TWC-3 code represents,  Two cycle, Water Cooled, type 3 formula.  The formula 3 has decarbonizing additives designed to be more compatible with the newer non-leaded fuel.

You can spend your money & purchase non synthetic OMC oil, or any other outboard manufacturers oil for about $6.50 a quart, or buy a name brand quart for $3.49.   Synthetic oil is about $8.50 a quart.   Sure the manufacturers want you to buy their oil, & for a new motor under warranty, it may be advisable to do so.   But the consensus from many experienced boaters is to use any good brand of oil for normal boating needs, as long as it has the TC-W3  rating, it meets or exceeds the manufacturers specifications.  Large motors pushing a heavy load for extended periods of time, or smaller trolling motors idling for extended periods of time may be something different & looking into the blended or synthetic oils may be beneficial here.  

Some dealers may try to tell you that new motor warranties are void if oils other than original manufacture brand oils are used & a internal mechanical failure happens.  There was a court ruling on this several years ago based on the Magnuson/Moss directive.  This ruling was that for this requirement to be valid, the manufacturer/dealer MUST supply the required oil at no cost to the consumer.  The "law" basically says the manufacturer can't specify a BRAND NAME of oil, unless THEY provide the oil.   However manufacturers can specify certain grades, (TCW-3) etc. and deny warranty work IF those specific oils are not used.  It is very difficult to argue that cheaper certified TCW oils don't give long life for the average boater -- there are too many motors running out there that say it does.  However it is hard to compare one owners usage with another owners, even using identical motors because of how hard the hand is on the throttle.

Outboard motor gas should probably NOT be ARCO brand, which usually has 10% alcohol in it & is actually called gasohol.  This alcohol additive may soften your fuel lines, fuel pump diaphragms, carburetor gaskets & not be compatible with some current outboard motor needs.

So you are really at the mercy of the oil companies in trying to decide just what they are saying in their advertisements.  Lots of talk at times, but not really saying much that is understandable.

In the old days, less standard oil than recommended in the fuel makes the engine run leaner and warmer (less power, causes detonation, & overheating, but more important, could cause the motor to seize up), more oil makes the engine run rich and fowls plugs (less power too), forms carbon deposits & friction can increase because of the carbon builds up, so more heat is also made.  Therefore a happy medium needs to be achieved depending on your usage.

If you try to lessen the oil ratio, and yet run it at higher speeds, you then will possibly run into other major internal problems.  This may not only be for proper crankshaft / rod bearing / piston wall oiling, because 2 strokes burn hot when run lean  & you can likely get a partially melted piston top in the lower cylinder.  To avoid this possible damage, and a melt-through of the complete piston top, you need to be aware that this can happen on a lean condition.  If in doubt, the safe solution is to run the correct fuel to oil mixture ratio of 50-1.

Outboard Oils:   There are very few subjects that stir the emotions of the outboard motor user more than to ask, "what 2 stroke oil do you use and why"?

Two cycle oils compose from 50% to 95% of the total weight of the 2-stroke engine oil.  They fall into 2 general categories: synthetic and petroleum based.   Since synthetic oils are not manufactured from petroleum, there has been a lot of questions flying around in the last several years about what really constitutes a ‘true synthetic’ oil.  There is no universally accepted definition for synthetic oil.   Each manufacturer is free to label their product "synthetic" by whatever rules the manufacturer chooses.   Also what exactly is a blended oil?

Due to the nature of the carburetored two cycle marine engines, fuel is mixed with oil which then lubricates the engine parts as it passes through the engine during the combustion cycle.   This is in contrast to four cycle engines which have oil sumps and pumps for lubricating the engines, and the fuel is not pre mixed.
 

The long term objectives of the two cycle engine industry have been to reduce emissions which contain burnt and unburned oil that has passed through the engine, and to develop a quality of oil that reduces the mixture ratio to fuel while extending the life of the engine.   That means significantly reduced emissions to satisfy EPA requirements, less warranty problems, and increased customer satisfaction due to engines lasting longer with less maintenance and overhauls.  Now 2006, with the new Federal EPA emissions standards for outboard motors being kicked in, even more emphasis on a better 2 cycle oil is needed.
 

TC-W3® lubricant, an NMMA owned trademark, has evolved over the years through much testing and research, and has proven to be the level of quality to satisfy the above objectives. And, going a step further, now that two cycle engines have moved towards higher cylinder temperatures and compressions, this lubricant also meets the EPA emissions reductions.
 

You will find some 2 cycle oils now that say they are a synthetic blend.   Just what does that mean?  What percentage of synthetic is mixed with the standard petroleum oils?  They are probably better than the standard oils, but how much?  How close are they to the synthetic oils?

Most all normal 2 cycle outboards today are recommended at a mix of 50-1.  That is 50 parts gasoline - & 1 part TC-W3 oil.  This standard was set when there was no synthetic oil on the market. 

There appear to be at least two on the market, (1) (AMSOL Saber brand) marine 2 cycle synthetic oil that is recommended at 100-1 & they say it produces less contaminates.   I would hope so.  The cost is about double that of the standard oils, but the benefits could be worth looking into especially for the trolling motors.

Amsoil synthetic outboard oil with a recommendation of 100-1	Pennzoil Marine 100% synthetic	Pennzoil Marine synthetic blend

(2) (Pennzoil Marine 100% synthetic 2 cycle) appears to be a more economy oil that is usually stocked at West Marine & Wal-Mart stores.  From what I read off the bottle in the stores, Pennzoil does not really toot it's own horn & this does not really inform the boating public well.   And going on their website does not expand your knowledge much either.  I have not had the chance yet to talk to a knowledgeable salesman, but the price seems to be less than & easier to obtain than the Amsol brand.

I am sure that there are probably others on the market if you look far enough.

Gearcase Oils:   The same debate as for 2 cycle oil somewhat carries over into gearcase oil.   Here I have to pull for the synthetic over the standard in that the synthetics are slipperier & therefore should give you better lubrication on the gears.  For those of you who are not a outboard mechanic, outboard gearboxes have all the gears revolving all the time the motor is running,  just that the sliding clutch dog engages either the forward or reverse when the shifter lever is moved in the desires location. 

To tell which oil is in the gearbox, if it has not been left there forever, usually the standard oils will be a more golden color, while the synthetics will be a bluish color.  The synthetic usually also has a distinctive smell.

This started out to be an informational article, but it seems that I have about as many questions than I have supplied answers.

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Originally started 02-02-2007, Last Updated 02-06-2007
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