2 stroke oil has disadvantages.

[a64pilot]

I thought a little about it, I believe I would if I had to run cooking oil, over four stroke oil and run it rich, like 25 to 1.
But only if I had to and I’d likely run at lower power
The Hi-point facing oil I ran in my Husqvarna back in the early 70’s was “pure vegetable racing oil” that’s what it said on the can anyway

Then many ran Castor bean oil, which did create a lot of carbon, gum and varnish, but was supposed to keep the engine from seizing better than anything.
Then I believe many rotary aircraft engines during WWI ran bean oil, it’s why Castrol oil has that name, they were a big Castor oil brand, and had a total loss oil system meaning the oil ran though the engine and ran out, no circulation,so of course everything was oil soaked, the engine cowls were open on the bottom in the hope that most oil would come out there.
Pilots were very often sick and throwing up at the end of a flight, that and likely freezing too.

[flyingfin]

JohnEngineer: Are you joking or completely clueless ???? All older two strokes should be run ONLY on TC-W3 oil, newer injected two strokes need even more advanced lubricant. Your only outboard must be a 2hp Seagull that was made 40 years ago.
Your Chemist buddy has been inhaling too many VOC's

[mikedefieslife]

Well some engines like the older 2t Yamahas use a 100:1 ratio not 50:1

At such small quantities a good bottle of 2t oil is hardly going to break the bank.

[wsmurdoch]

The owners of the trademark TC-W3 have a web site
https://www.nmma.org/certification/oil/tc-w3
That has links to several papers on what oil manufacturers must do to meet their specifications and earn the right to use the trademark.

My old 1968 Evinrude's manual says, "If Evinrude Outboard Motor Oil should not be available, a good quality outboard motor oil or SAE 30 automotive oil may be used. The oil used should have Service ML-MM or Service MM marked on the container. Additional markings such as MS, DG, DM, DS, designate heavy duty and should be avoided. Also, low priced light duty oils (container marked only with ML designation) and multiple viscosity oils (SAE 10W-30, etc.) should not be used,"

Both my 3.5hp Tohatsu and my 8hp Nissan say in their manuals, "Use genuine engine oil or the other recommended one, that is, TWC3. We can not recommend any other two-stroke engine oil."

Of course, they could all be wrong.

[John Engineer]

My replies,
Firstly I will explain the basics about 2 stroke fuel mixture adjustments when I re-design engines etc.
The 2 stroke motor has been around long before me and most of you readers but the concept is still very similar today.
The higher the inlet and exhaust port the higher the design RPM of the engine.
All exhaust systems Motorbike or outboard etc. have a measured length of varying shape exhaust pipe that is especially designed to return a pressure wave back to the cylinder just before the piston closes it. (All calculated by the speed of sound.)
An outboard propeller is designed to turn at a maximum RPM just before causing too much drag or cavitation, so engine design speed is paramount with prop diameter and gear reduction etc.
Racing outboards is costly and complicated to get right.
EXAMPLE Below.
Tahatsu 2.2 Hp 2 stroke. that planes a 6 man Zodiak wit 3 people in it at about 12 knots. RPM about 10,000
The prop diameter was cut right down to reduce tip cavitation. Epoxy Filler was inside the crank case to increase fuel transfer pressure. Raised + wider inlet & exhaust ports. Reduced squish band (Lower cylinder head) Welded aluminum to reduce combustion chamber area. Flat face high compression plug. Flap cone inside exhaust to return pressure wave to suite new higher RPM.

So now the fuel side.
The carburettor was opened to 13mm from 10mm and the reed valves were enlarged.
Result was a screaming high performance outboard that sounded like a race car and totally un-practical for the average "yachtie"
The fuel mixture is the live or die reason to such extremes and I have paid the price more times than I can count.

If you lean the fuel out there is a graph that shows the power output increasing for less fuel until the flame out point of too much oxygen.
Lean fuel also means lean oil so you need a high enough ratio about 50:1 (not above 100:1) to cope with the lubrication required for crank bearings and cylinder lubrication during this higher temperature and more economic or perfect situation.

This flame out point on the fuel mixture graph drops off like a knife from full economic power to stopping. (wont ignite the fuel)

So Manufacturers have to play a little safer and make the fuel jets slightly bigger than the perfect lean point. There two advantages to them doing this.
The first is that the motor always has plenty fuel at full power (or low)
It also ensures plenty lubrication at lean oil mixtures like 100:1

The draw back is that the customer uses more fuel and does not achieve the full potential power or smoothness that is found at leaner mixtures.
2 stroke jet-skies and Evenrude/ OMC family had low and high speed adjusting screws to overcome these known problems.
Now there are less engines that offer these fine adjustments.
So the reason I use SAE30 normally (Or my regular diesel engine oil) is because it was found to protect my engines under extreme conditions.
Many years of actual tests and expense to improve any performance or reliability is always the goal.
--------
As for the people that know far more than me? They is always those that know more even if they have little experience in paying for mistakes like me.
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My reply to:
Bill Seal:
You asked about motorcycle oil?
Well the 2 stroke oils are basically the same by my past experience however motor cycles have some differences in exhaust and combustion temperatures generally.
There is probably a viscosity and flash point difference that I have not studied?

Excess oil or heavy SAE 80/90 can cause the top of the exhaust port to carbon up every few hundred hours. So thats why I like to use oils that are not too thick and still burn but don't evaporate under high load or crank case and cylinder temperature.
All oil injected (auto lube) engines are free from this carburettor varnish problem.
I used to race a Yamaha RS195 twin cylinder and I melted about 5 or 6 different pistons before I found the trick.
Although "auto lube system"
When the motor was at full throttle the motor never failed (2stroke oil) but as soon as the power was removed and slowing down. The motor was hot as Hell the lack of fuel (and oil inside for bearings etc) caused the air cooled motor to run extremely lean without sufficient lubrication and the pistons would burn to the cylinders and blow a hole in the centre of the pistons.
When I spoke to other racers they explained that at high temperatures (and 15,000 RPM) the 2 stroke oil was burning off the cylinders and that was the cause.
I started using SAE 30 and never had another piston failure again. This oil has a tendency to stick to the cylinder wall better and NOT Completely burn away as 2 stroke oils are designed.
So I agree that 2 stroke oils burn away better but leave less cylinder protection.

Outboards however come to a idle speed very quickly and a rich idle mixture normally stops any of these extreme conditions. The RPM is normally below 5.000RPM too so 2T oil or SAE 30 at lower temperatures have both worked well for me.
High HP output engines have higher temperatures and require oils to maintain cylinder protection (+ crank case bearings)
Lake-Effect:
Using two stroke oil in an engine in the way you use it should be fine and everything should work fine every year? The point is that you don't store old fuel or leave it inside your float bowl to evaporate everything leaving sticky varnish solids.
Water cooled 2 stroke engines normally are cool enough to maintain good lubrication using any GOOD 2 stroke oil.
Let it stand in a hot place for a month and the whole reliability thing changes fast!
So if everyone does this (Don't leave any fuel in the fuel system) then 2 strokes carburettors should be as reliable as 4 strokes!

Those of you who prefer to follow the flow to insult me or even chemists higher qualified than most of you?
Please ignore this post as this is for those NICE PEOPLE that are trying to resolve a yearly or daily problem with 2 strokes that have fuel complications in whatever manner it might be.
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My reply to:
a64pilot:
Vegetable oils were indeed a big thing as Castrol "R" for racing was very popular in UK back in 1950's to 70's
I used it for a couple years too with no problems in motorbikes.

This test below was done purely for testing reasons to a clean engine.

I have done a couple months trial (about 100 hours use on a 8 hp Suzuki outboard) in the 1980's using regular sunflower cooking oil.
The engine smelt like I was cooking fish and chips but it did not do any structural mechanical damage.
When stripping everything down I found bearings and crankcase area was clean. Fuel transfer port also clean. Spark plug with heavy carbon deposits as top of piston starting to get dirty deposits.
The top of the exhaust port that is well cooled attracted a lot of the solids and carbons as the water cooled motor caused this to attract the escaping particles.
Carburettor and fuel system had no problems.
I do NOT recommend COOKING oil for the reasons of the exhaust port slowly becoming blocked (and "the sea gulls looking for the fried fish")
However vegetable oil works fine at 50:1
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My reply to:
mike'defies'life:
The cost of 2 stroke oil is NOT a problem in general. I agree.
100:1 motors always say 50:1 when you get them new and after the guarantee is gone you can reduce the oil to help environment. On water cooled motors this appears to work OK but you do notice the reduction in power at full power after a while. (Less oil = less sealing of compression rings)
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My reply to:
wsmurdoch:
I agree that a mono-grade is better than multigrade oils.
As for ALL 2 stroke oils being bad? Maybe not so?
Maybe there some newer 2 stroke brands that are working on this "varnish after evaporation" problem that many boaters experience.
Progress is bound to happen with tests and chemists trying new formulas.
I am just unaware of this breakthrough whilst also retaining high quality lubrication.
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EXPERIMENT FOR THE SCEPTICAL READERS.
TO PROVE "2 stroke oil has disadvantages"

If you take 2 empty jars (or more) and put a measured amount of 2 stroke oil in them except 1 jar that you put any normal engine oil into.
Object is to have 50:1 (or 100:1) oil/ gasoline mixture in them.
PLEASE MAKE SURE THIS IS IN A SAFE PLACE AWAY FROM SPARKS etc.

Most of the fuel will evaporate within a few days and just the oil is left.
If left for a month or so in the sun you will notice that the engine oil stays unchanged but the 2 stroke oils normally have a varying thickness until they dissipate like they are designed to. The SOLIDS that are left resemble what you find inside your carburettor and fuel tank each season.
If you like? You can add an aluminum pot scourer or cooking foil inside to see how it sticks to it.

If your 2 stroke oil stays in the heat after a couple months without changing its ORIGINAL properties then I would use that myself.

My 30Hp Yamaha from 1996 still has a very good compression and quiet crank bearings like new. It must have over 1000 hours on it now.
I used it every day as my taxi in St Maarten at about 40 knots for 5 years and still well.
I Prefer to learn by the mistakes of others but I have had to make a lot of my own to be sure I was wrong! That's wisdom.

[liquidice]

I’m a huge fan of this thread and the OP. I got into outboards due to the need to push my sailboat out of the harbor safely and reliably. Over the years my continuing search for the ideal outboard (plus one backup) has matured into a hobby business as a buyer seller and repairer of small outboards, with a focus on sailboat propulsion. It has a lot going for it as a hobby, such as small modular high value units, relative availability of parts, high price and restrictions on newly manufactured or imported units (4 strokes only in the US), large numbers of durable old OMCs coming on market continuously as garages are cleaned out, and they’re repairable. I’m in Chicago so for now sailing is seasonal for me and tinkering with motors keeps me busy in the winter.

Thanks for sharing your knowledge. You mentioned an omnibus of sorts; I plan to read it if links are available. Your explanations are enlightening and I find many of your arguments compelling. Again, thanks.

[Lake-Effect]

Originally Posted by John Engineer

My replies,
...
Lake-Effect:
Using two stroke oil in an engine in the way you use it should be fine and everything should work fine every year? The point is that you don't store old fuel or leave it inside your float bowl to evaporate everything leaving sticky varnish solids.

Actually, I don't often run my carb dry after use or at end of season... though the way it gets transported and stored maybe drains the carb. It's bad practice in my book to store and use old gas, period. Given the way good 2-stroke oil dissolves fully in gas, and based on my personal observation of zero insoluble residue, I'm fairly confident that for the normal profile of outboard user, there is no downside or danger from using good 2-stroke oil.

I have no reason to doubt that you have much more experience than I with engines, and you may be a valuable resource in this and future outboard threads. But your poorly qualified claim in a cruising forum that "2 stroke oil has disadvantages" is kind of irresponsible. We don't often engage in outboard racing here; maybe that's the difference.

[John Engineer]

Thanks to "LIQUIDICE" & "Lake-Effect". Fair comments.
firstly I wish to address the "Shell Nautilus 2-stroke oil" that was found to leave NO residue like varnish (I read it wrong the first time and thought the fuel system was fully drained after use)
Well then? Maybe you have found a GOOD 2 stroke oil and they DO exist and it's possible that there are many other 2 stroke oils out there that are responsible for "DISADVANTAGES from varnish residue"
I would like to hear comments from other Shell Nautilus 2-stroke oil users to see if there is a genius in the shell oil company?
It's good news by what I read from Lake-Effect however only the long term tests results would give me confidence to use it. (worth a test on high temp air cooled as well)

Reply to "liquid'ice"
I can't see where I mentioned an "OMNIBUS" but maybe you revered to many things I pointed to?

Because of using SAE30 mainly as my lubricant and knowing I never seen any varnishes yet!!!!
When I stop my engine for any length of time ("Over night or for the Season") I want all my bearings inside the crank case + piston rings to be well lubricated and coated with oil.
Also knowing that the air surrounding outboards is normally about 98% humidity and often "salty air".
Manufacturers are aware of this so a stuff like "FOG" or similar brands came out to spray into the carburetors while running to coat all the inside parts before stopping.

I have never bothered to use this method as I just open the throttle and pull the choke to flood my engines with the fuel mixture I am using. After about a few seconds the motor normally stops from over fuel and that's it.

1/2 hour later or a year later i have found that the bearings / piston/ rings are still protected with oil and compression is perfect at first pull.

As opposed to running your outboard totally dry in the sea water or via soapy clean water before it stops.
The nice hot exhaust has a lovely misty steam inside after it is stopped.
(Good for an outboard business)
If the piston (or one of them) has stopped anywhere near the bottom (as normal) with the exhaust and inlet port open?? then that nice steam will stream upwards (normal convection) towards the crank case and deposit it's minerals onto the surfaces.
So for the readers that have put a perfect motor away for the winter as perfectly dry and washed clean!! You might find a slightly noisier motor each season as the moisture content is allowed to attack the perfectly clean bearing surfaces inside.

By stopping with a "FOG" (non evaporating oil based spray) (Not WD40) the surfaces are better protected.
Or if you use a motor oil in your fuel that you leave without draining the carburetor then the float needle and jets also has this oil film protection too.
Shell Nautilus 2-stroke oil might be the answer for those that only with 2 stroke oil.
THIS SHELL BRAND I have not tested exhaustively but engine oils like SAE30 I have.

I hope my in depth detail has helped some of you. If there is MUCH MORE that you need to know about engine design then it might be best to open another post regarding design Crank case compression /exhaust lengths/ Piston speeds / Limits / and so much more that I only tipped the ice burg on this subject.
Regards to you all.

[motion30]

interesting that mercury marine Yamaha nomc Corporation spent Millions researching 2-stroke oil and we have the whole issue solved here on cruisers forum amazing to. I guess the out board manufacturers should have come here first and saved lots of money

[Adelie]

This is almost as much fun as a COLREGS thread.

[skipmac]

I have a degree in engineering but don't know beans about how to build a house or factory or how to calculate power losses in a high voltage transmission line but can talk a lot about IC design and fabrication.


Same applies to chemistry. Someone that works at an oil refinery may know a lot about refining crude oil, distillation columns and such but does not necessarily mean that person knows anything at all about combustion of oil in a two stroke engine. I sell chemicals and know several chemists and chemical engineers, one that specializes in distillation and petrochemicals. Last week I asked him about recommendations or risks for making an aqueous solution from the crystalline form of an acid, a simple process I thought (as a non chemist) and he didn't have a clue.


Your friend may have studied this application on the side or maybe he/she used to work for a motor oil producer but unless I heard more about his/her expertise in this field I would stick with the recommendations of the engine manufacturer,

[MarkSF]

My understanding is that marine 2-stroke oil has additives to help speed up biodegradability in the environment. It's also meant for lower combustion temps than regular 2-stroke oil.

As you're already running a really filthy engine, it might be nice not to make it filthier than you have to.

[model 10]

You can still get the castor bean smell with a modern oil. Castrol A747 is racing 2 stroke syn and castor bean oil and it smells better than the old oil! $20 qt.

[motion30]

remember when these motors were new the manufacturer had to honor a warranty for at least a year often longer. they had a different interest in you using the proper oil. if you ever worked on many two strokes. you could tell quickly on this assembly if the customer use quality oil

[John Engineer]

Hi MarkSF.
In reality I agree as we all need to do our part to protect the environment so if the biodegradability of 2 stroke oil reduces harm to environment compared to any other oil that I say increases reliability it makes no difference.
2 strokes are filthy and you are right.
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A different subject directly related to pollution from us is how we make electricity where we live and the car we drive. The carbon foot print we leave.
The diesel engines in our yachts with very inefficient propellers that turn far too fast and waste more than 50% of the mechanical energy available as an average.
This is not an to say MarkSF is wrong! Its to say he is right and the reliability of 2 stroke engines should be less important in our selfish lives.
I prefer to talk about how to make the world a better place to inherit after we are all gone!
Cheers John.