I spent some time at the library researching lubrication and engine wear in internal combustion engines. A great reference is the volume on tribology and wear of the Metal's Handbook for those interested.

For best engine break-in, you should run a richer oil ratio and light engine loads. Just like the engine manufacturers recommend. You should not run the engine at full throttle for extensive time during the break-in.

The reasons are as follows:

There are 3 regimes of lubrication.
1. hydrodynamic
2. mixed
3. boundary

If you have a complete oil film separating the parts, then there is no metal contact and zero wear. This is hydrodynamic lubrication - an example is a journal bearing with high pressure oil between the parts. The hydrodynamic regime is favored by light loads and high speeds.

If there is an very thin or incomplete oil film separating the parts, the high points of the 2 metal surfaces contact and wear away. This is boundary lubrication. Boundary lubrication is favored by heavy loads and low speeds.

In between these two regimes is the mixed lubrication.

The piston, ring and cylinder operate under conditions of hydrodynamic, mixed, and boundary lubrication depending on the load and operating speed.

A new engine has an imperfect fit of the ring to piston and cylinder wall. The ring has not yet achieved its best shape to act as a gas seal for hot combustion gases or to best transfer the heat from the piston to the cylinder wall.

The purpose of the break-in is to wear away the high spots on the ring and cylinder to give the best gas seal.

If the engine load is too high during this break-in, the ring is pushed toward boundary lubrication, which can tear away the metal by burnishing or galling. Once the metal is burnished, the gas sealing and heat transfer properties of the ring will never be optimum. The engine may run OK, but it won't run as well as it could have with a better break-in. Running an engine under high load during the break-in can also contribute to an increased potential for seizing. With a marginal gas seal, there is more blowby, more piston heat, and poorer heat transfer from the ring to the cylinder.

Light loads and a higher oil ratio during break-in push the rings and cylinder toward hydrodynamic and mixed lubrication. The wear on the rings occurs by micromachining away the high spots a little at a time. The excess oil also helps to flush away the wear particles. The light loads also minimize the temperature rise of the piston and minimize the amount of heat that has to be transfered from the ring to the cylinder. Once the ring, piston and cylinder are properly broken-in, the ring can make a good gas seal to minimize blowby, and can also transfer heat more effectively to the cylinder. Now the engine is ready to handle high loads, high power, and temperature.

If anyone has a problem with this information, please contact the Society of Automotive Engineers. I'm sure they would like to hear your theories.

I have read more than once that engines wear the most after start-up and while they are getting up to operating temp. My theroy is the faster you want a engine to break in is start it up and run it up to running temp and let it cool down and repeat this as much as possible. Ever hear the saying" the more I run it ....the better it runs....like after many start ups and use. Diablo you gave us some very good facts, I am sure you love engines maybe more than flying????? Best Regards Captinjohn

A L L A H

I agree captinjohn.A picture paints a thousand words or in this case/the volume on tribology and wear of the Metal'sHandbook .Sounds all fine and dandy but nothing and I mean NOTHING beats first hand experience and hands on!!!!!!!!!
Besides that book is probably as old as the dinosaurs. Things are differen't these days and products change and so does the way we do things.Things that were proved years ago aren't necessarily the right way to do things today.
Sounds to me that the hundreds of guys out there including myself that are breaking in motors with synthetic super oils are dumber than a box of rocks just because we don't agree with the scientific book on breaking in metal.
Besides scientist didn't invent these model airplane motors,guys like you and me did,and guys like you and me regardless of what the manual says-------------- know best!

The Metals Handbook is the latest edition, written in the last 5 years. The SAE papers referenced at the end of the 3 chapters include papers written in the last few years on the subject. As we say in the science biz, the data doesn't spoil with age. The data and conclusions are drawn from scientific studies by the folks that design, manufacture, and test engines and lubricants for a living. Folks like Ford, GM, Lubrizol, etc. Despite what some may believe, engines work just about the same as they always have - the science and engineering haven't changed significantly.

But hey, if you guys think a lumberjack from the North woods is a better source of information because he uses a chainsaw for a living......well knock yourself out.

Captainjohn:
You are correct about engine wear being greatest during startup. The reason is for a pressure fed oil system, there is no hydrodynamic lubrication of the journal bearings on rods and crankshaft when there is no oil pressure at startup. The bearings see boundary and mixed lubrication which causes higher wear. If you had an electric oil pump / preoiler on your car engine and could get the oil pressure up before you started the engine, the journal bearings would NEVER wear out. They might corrode away eventually, but not wear away.

For a 2 stroke engine with premix oil and gas and all rolling element bearings, things are a bit different. Rolling element bearings require no break-in. They are good to go after being manufactured. The only thing we need to break-in are the ring, piston and cylinder wall fit. And the best method for that is described above.

nobody said anything about lumberjacks! Were talking about hundreds of rc guys like you and me that fly radio control models.I will take their advise any day over a bunch of words written in any book. As we all know the directions that come with our motors state we should run this size prop and get these kinds of rpm's when in reality that seldom happens.We all experiment with differen't props and such to see what does best for us. If there are people out there that go by the book we know they are depriving themselves from better things and that's a fact I don't think anyone can argue with.
As far as the info on the book, it's probably good reading,but it's not going to convince anyone to change what they know to be best for them.I'm not saying what the book states is wrong,I'm saying that for some of us who have experimented with this process have found a better way to break in an engine with synthetics,atleast for the guys who have ventured away from the norm that is.

Absolutely correct. Books are very dangerous things.....

Never ever admit to anyone that you have read one. They might change their opinion of you.

exactly stated!!!!!!!!!!!!!your knowledge from books may indeed change one's opinion of you.-------------------read too many books though, and you'll never learn anything for yourself.

A common statement when I was going to school was:
" A smart engineer knows in which book to find the correct answer."

A poor one, doesn't bother to look and tries to reinvent the wheel.

Diablow: I was thinking every car engine that rattles on startup should have a push button electric oil pump just to get the oil up so the cam chains ect will not rattle. My Ford explorer is a typical example. Read on the auto websites how many have this problem........ Now back to our RC engines.... I should say the piston, sleeve and rings is what really needs the break-in process. Many start ups is what I think helps this. As far as reading what you print here....I think it is great.... that anyone that takes time out, to look up and print how this breaking a engine in, or helping tune it...should be praised more. After all, helping one another is what it is all about. Love it. Captinjohn P.S. I did not major in english

If I may point out a few thigns that are not being considered here. . First off. . Fryfly, you are DEAD wrong, and you need to learn a few thigns about metallurgy, oil properties, wear-in of closely fitting parts, and what exactly goes on inside an engine before you start lambasting engineers and people who study these things for a living. I've read dozens of your posts on other subjects. You are nothign but an uninformed instigator and problem child. . please remove yourself from this discussion.

Now. . concerning wear-in of parts in the reciprocating assembly of an engine, specifically the piston, rings and cylinder bore. . . It IS necessary to have some "shearing off" of high spots to achieve optimum ring-cylinder seal. what EVERYONE forgets is that the "seal" is nto accomplished by direct metal-metal contact, but by the OIL that is mixed in with the gasoline. . This is true for every piston engine out there. The best seal is achieved with "almost" perfectly polished parts, but NOT perfectly polished parts. . WHY?? Because, if you have perfectly smooth surfaces, there is no place to hold the oil that is necessary to make the hydrodynamic seal between the ring and cylinder, the oil gets wiped off the surfaces, and blow-by occurs. Even hard-chromed cylinders, with extremely smooth plated surfaces, have microcracks in them in order to retain oil for lubrication and sealing purposes.

How best to achieve this "matching" of piston, ring and cylinder wall? Well, first off. . you do NOT want to wear on the piston. . it's soft aluminum and any adverse wear on it can gall it and make it drag as the high spots rub against the cylinder wall. So, you want the piston skirts to remain as smooth as possible so that their large area "floats" on the polished bore. this requires high amounts of lubrication while the cylinder and ring are wearing in to eachother. Notice I said AMOUNTS, not meaning lubricity but actual physical mass. You need this oil so that the piston can float on it as it glides up and down the bore. What you do NOT want, though, is to over-lubricate the ring-cylinder interface, which means you need a large amount of oil for the piston to float on, but it shoudl ahve a low shear-strength so that the ring can displace enough of it to wear against the cylinder properly as they polish eachother. that being said, using a high sheer strength synthetic oil is a BAD idea during break-in, since it's high film strength will actually prevent the ring-cylinder wear necessary to polish them. The use of synthetic oil has, therefore, an adverse affect on what you are trying to do while breaking an engine in, while using a petroleum based oil (with lessor film and shear strength) in higher concentrations will achieve exactly what you are trying to do.

Now, after the break-in period, usually 10-15 gallons or about 4-5 hours of run time, we no longer want to 'wear-in" the ring-cylinder interface, since 90% of that process has already taken place. What we want NOW, is to utilize the finely matched piston/ring/cylinder we have just achieved, to its greatest potential, and this is where synthetic oils excel. You can use them in lower concentrations, allowing more gas than before (and adding to the power slightly), they withstand impact and shear forces better than the petroleum oils, so they will protect the engine better under rigorous use, and with their thinner consistency they will have less overall drag on the internal components than thicker petroleum oils, thus slightly increasing power. Also, since synthetic oils do not "burn" as much in the combustion chambers, but remain in a lizuid state for the most part, they will carry away more heat in the exhaust gasses as they exit the engine, helping to keep the engine cooler than petroleum based oils.

The SAE is right. . I don't care what blow-hard bench-engineers at the flying field may say otherwise. Teh "professionals" at the SAE have looked at things and studied these problems for generations .. I'd trust their judgement long before a fellow modeller who tries to contradict them.

Dub Jett, master engine builder at Jett Engineering... a man with his share of RC experience and engineering degrees says:

http://www.jettengineering.com/tech/breakin.html

Quote:
"There are more ways than one, but it is important to remember one thing: With an ABC or AAC engine you don’t really have to worry about breaking in the piston and liner as that will take care of itself. The rod and crankshaft journal pin fit is the object of the break in...."

Does the advice never end?

I know I know... he's talking about ABC, this debate seems to be about ringed engines (except for captinjohn... who was talking about ABC)

So who is DEAD wrong and who is DEAD right? I think nobody.

Remember Machiavelli's words:
There is nothing more difficult to take in hand, more perilous to conduct, or more uncertain in its success, than to take the lead in the introduction of a new order of things. -- Niccolò Machiavelli, "The Prince".

There should always be room to question conventional thinking.

well then I guess you guys are right! still won't change my mind though on how to break in an engine.If you wan't to use that way to do it then fine no problem.As for me I'll keep on doing it the way the backwoods chainsaw boys do it as Diablo stated earlier.I'd still listen to the guys that run the engines instead of guys who don't (rc engines that is ) not anything else. But that's just me.
also I never said that anything you guys have brought up in discussion is wrong!!! NEVER once have I said that.I have only referred to a way that many others in their own observations have proved to work better for them.I have never Bashed any one person for the way they do things,only a suggestion to try something new.
However kris on the other hand pretty much has said in his last post that everything I have stated is wrong and I'm misinformed and personally has attacked and asked/told me to leave this discussion because I don't know what I'm talking about. If you can prove me wrong on anything I have said then fine but everything looks good on paper. Sounds to me like you guys don't except anything unless it's on paper.
Like I said before I never called ANYONE a liar and never have, just a suggestion on a differen't way to do things that has been proven to work.

Jim, specifically, in this case, we are talking about gasoline engine break-in, not glo or ABC/AAC/ringed glo motors.

Jett is correct in his assertions about the non-ringed ABC and AAC engines. They have a lot of clearance along the bore and then close up near the top for better sealing during combustion. But, remember. . these glo engines use 20%!!! oil content in the fuel, not 1-2.5% (depending on pre-mix ratio) like our gassers use. Things get a tad more critical in our case, I think.

Jim: Read post# 10. I mentioned rings that ABC engines do not have. This is a giant scale forum, and I have not seen too many giant ABC engines. That leads to a very interesting question..... why are bigger gassers not abc??? Thanks Captinjohn

Hi Jim:
You quoted from Machiavelli -
-----------------
Remember Machiavelli's words:
There is nothing more difficult to take in hand, more perilous to conduct, or more uncertain in its success, than to take the lead in the introduction of a new order of things. -- Niccolò Machiavelli, "The Prince".

There should always be room to question conventional thinking.
-------------------

The scientific method has no problem with questioning conventional thinking. Someone comes up with a new theory, and then devises an experiment to test the theory. A new theory without any evidence doesn't have a whole lot of value.

One last example. You go to a Dr. and he tells you your appendix should be removed because it's inflammed and that's what's making you feel lousy. Would you ask the opinion of your flying buddies on what you should do? After all, they all have an appendix, don't they? Ownership of something doesn't make you an expert on it. For a 2nd opinion, most people would go to another Dr.

I have to jump in on this one , all of the replies are very
interesting only because I don't , (for the most part)
disagree with anyone. ALL points seem to be valid.

I will usually run two tanks of fuel at a light load and low
rpm on the ground , then just fly it on the fat side for a few
flights then lean it for the best reliable running, (not tweaked for every
last rpm)from then on. Why am I telling you this? Only to show
that I do at least some break in, does it matter ? probably . But
in some cases maybe not .

Consider this, How many chainsaws,snowblowers,lawn mowers,
weedwackers,etc,etc,etc do you think get" broken-in"? And yet
these machines run for years.

If you got a brand new snowblower today , and then got
12 inches of snow tomorrow, would anyone reading this
use a shovel because the motor isn't "broken-in"yet ?

Fill the oil,fill the gas, wide open throttle, GO !

Just another point of view
Roby

gee whiz... I lost track of what forum I was in! forget that glow stuff!

I dont have any thing to add,not really .We are all doing this for fun,RC flying. Is not the increase in power partly due to reduced friction after proper breakin?
Kent

Hey Roby, welcome to the debate!!..

Good point BTW. . but you have to remember that these weedy/blower motors are set up with Nikasil cylinders for fast break-in, you are running 32:1 -40:1 oil ratio on petroleum based oil (usually) and even under the most rigorous conditions they seldom see the loading adn heat concentrations that our model engines do. these engines are built with mass-produced looser tolerances as well. . ever pull down a Ryobi leafblower motor and take a peak inside? the ports look like they were made with a hatchet, the crank counterweights are multi-plate pieces, and the bearings have a ton of slop....hardly "precision" but it's what keeps them alive for 1000+hours of usage. "Break-in" occurs with them very quickly, and the nikasil cylinders and loose tolerances are very forgiving of dirt, heat, and abuse.

OUR engines, like those of 3W, DA, and BME (with its new cylinder designs) are totally optimized and close-tolerance engineered pieces designed to eek out the last Nth of power and performance whiel giving exceptional longevity and durability. Proper care and break-in is essential to get the most out of them. A "weedy" motor costs about $50. . how much does one of OUR engines cost? Taking the time to do a proper break-in of these expensive motors just makes good sense. Personally, I want them to last 10 years. . it's gonna take that long to pay them off ! ! !

Don't know nuttin about no snow blower, but kinda makes you wonder what the old Briggs and Stratton <SP> would have done if it didn't get filled up and pushed off into foot high grass when new just to see what it will do. The only gas little airplane engine I hav eowned is a G23 All I am sure about on it is it keeps getting stronger and stronger. Guess it will break in one of these days. Been in on the breakin on many others, and the ones that are treated gently to start with seem to produce the more power and have the fewest problems.
Ed M.

here is just a little reading material if anyone is interested Two-cycle engines are simple and have no lubricant distribution system to speak of. In pre-mix engines, oil is mixed right into the fuel, and in injector systems, oil is added to the fuel and air at a rate appropriate to conditions as the fuel and air enter the engine. In either case, the oil is simply mixed with the fuel to lubricate the engine parts. The reason two-cycle engines work so hard is simple: every stroke is a power stroke. In a four-stroke engine, the piston rises and is driven down by combustion (a power stroke), but the next time the piston rises it simply pushes out exhaust gases. In two-cycle engines, exhaust gas is driven out by the incoming oil-fuel mixture as the piston forces the mixture into the combustion chamber – on each and every stroke. These factors combine to place tremendous demands on lubricants:

Burn, and burn cleanly

Since the oil is mixed with the fuel, it must also be burned with the fuel, and burned cleanly. If you’ve seen the tell-tale blue smoke coming from an outboard boat motor or motorcycle, you’ve seen a case where oil isn’t burning cleanly – environmental regulations, concern for the environment and just plain common sense make that kind of scene unacceptable.

A more subtle danger when oil doesn’t burn cleanly is what happens to the engine itself. Deposits in a hard-working two-cycle engine can cause scuffing and ultimately engine failure. Even exhaust outlets can become plugged, and when that happens, engine efficiency drops and wear increases.
Resist volatility
Two-cycle engines run hot. But while the oil must burn cleanly at combustion temperatures, it must not burn at the hot temperatures found outside the combustion chamber. If an oil is not highly resistant to this volatile evaporation, deposits can begin to form and cause engine damage.
Lubricate
Two-cycle oils must lubricate effectively under these severe conditions. Failure to lubricate properly can quickly result in excessive wear and finally engine failure.
Assist in cooling
Two-cycle engines are either air-cooled (hotter) or water-cooled (cooler). In either case, the lubricant must take on a major portion of the cooling duties.
The Conventional Answers
Conventional petroleum lubricants use bright stock, a heavy cut of petroleum, to add lubricity and anti-scuffing properties. Unfortunately, bright stock doesn’t burn cleanly. In addition, petroleum basestocks are more prone than synthetics to volatile evaporation, and when they volatize, they tend to form hard carbon deposits that cause extreme engine damage.
To solve the contamination problems caused by dirty-burning bright stock, conventional two-cycle oil manufacturers use solvents to keep engine parts clean
When using low-grade solvents, however, there may be drawbacks to this approach. Low-grade solvents help with dispersency, but they can hurt film strength and ultimately detract from lubrication performance, and manufacturers that treat two-cycle oil as a commodity are likely to use bargain-basement solvents instead of the more costly ones that perform better..
To meet pumpability, mix ratio and low-temperature fluidity requirements, AMSOIL 2-Cycle Injector Oil uses only high grade solvents, which lead to its superior performance. However, as we’ll see, solvents are unnecessary in a high-quality pre-mix oil
.Finally, to deal with hotter temperatures, conventional two-cycle oils used in air-cooled applications must employ metal-containing (ash) additives to overcome weaknesses in their basestocks. Since ashed additive packages can cause fouling problems, these companies then formulate a separate oil for cooler water-cooled applications.
The AMSOIL Solution
The most striking thing to most customers about AMSOIL Synthetic 100:1 2-Cycle Oil is the 100:1 mix ratio. It’s unique, impressive and right in the product’s title.
Why can AMSOIL Synthetic 100:1 2-Cycle Oil be mixed at 100:1 while other products are mixed at anywhere from 50:1 to 32:1? It’s no mystery. The answer has to do with solvents, or in this case a lack of them.
Solvents often comprise as much as 20-30 percent of a conventional pre-mix two-cycle oil. However, AMSOIL 100:1 2-Cycle Oil uses a proprietary ashless formulation that makes use of esters – and no solvents. This technology actually delivers solvency characteristics while improving lubricity.
Since AMSOIL is 100 percent active, it can be mixed at the economical 100:1 rate. But the high-performance features of AMSOIL Synthetic 100:1 2-Cycle Oil don’t stop with the mix ratio:
The unique synthetic formulation used by AMSOIL is clean burning. The lower emissions you can expect are much more in line with what current and pending lubricant standards and environmental regulations demand – not to mention what our environment deserves.
Due to the absence of solvents, fire and flash points are dramatically higher. These higher flash and fire points help AMSOIL products resist volatile evaporation and allow a single, non-ash formulation to be used in both water-cooled and air-cooled applications. AMSOIL products provide enhanced lubricity. This high lubricity, in turn, aids in engine cooling (since much of the heat generated by an engine comes from friction) and promotes faster response, greater efficiency and improved overall performance. Ashless formulation has been shown effective in water- and air-cooled applications. AMSOIL Synthetic 100:1 2-Cycle Oil is perfect for both kinds of applications. The benefits of using AMSOIL Synthetic 100:1 2-Cycle Oil are clear: economical mix ratio, reduced emissions, less engine fouling, cleaner combustion, reduced smoke, greater efficiency, cooler running, lower volatility and improved performance.
AMSOIL ACTION NEWS / MAY 1997

elsewhere on Amsoils site and others it states Synthetics are ALSO recommended on new engines because the meet and exceed manufacturers recommendations.

since automobiles were brought up in this thread It might be interesting to know that both NASCAR,and the NHRA recommend using synthetic oils in their engines from the start (not broken in ) for superior performance and engine life.

After all aren't these high performance motors re run just as hard on parts proportional in size than any oil drenched/submerged 10 quart V8

I agree with most of that info, however I don't like running that lean an oil ratio. There are synthetics available designed to be run at 32:1 - that's still only 4 ounces to a gallon! These synthetics don't leave deposits at 32:1, and more oil will provide a better ring seal and more safety margin on a lean needle setting. More oil also ensures that the needle bearings get enough lubrication. There's no downside to running more oil of the right type, other than cost and cleanup on the plane. But, nearly all of the plane motor manufacturers recommend synthetic AFTER break-in with petroleum oil.

fryfly: Remember that Nascar engines are hand built and the internal part clearances are totally differant than our RC engines. I have to agree with many that say do not use the synthenic oils until the engine is run in somewhat with a good brand of fossile oil. Then go to the Amsoil type lube. Captinjohn Forgot to add... Diablo has a REALLY good point there. 32-1 lube has a real important advantage.... Lean run is not going to damage egine as much!

I agree but one more thing to think about
There are no standards on how long each engine breaks in at or to say seat the rings.One engine might take 3 gallons another 7 gallons.If all we are doing is taking out the microscopic metal pieces that need to be say--- rounded off.Then you should be able to do that in the first 2 gallons of fuel. Piston rings are made to expand with use and wear so by using a petro based oil you in turn after say 3,4,5 gallons are theoretically doing nothing but wearing down cylinder and rings. Petroleum based oils do not help in seating the rings but in turn force to seal piston and rings. Synthetic oils are not 100% wear proof and will aid in the process of seating rings also. One thing petro oil does or has is additives that create soot to help in the wearing process,by using regular oil the soot creates/takes up space between rings and piston wall constantly wearing down even after microscopic hairs break down and the piston walls and rings become smooth.
Why not from the start use synthetic oil as once the microscopic hairs wear,either 2 to 10 gallons of fuel the full protection that synthetic creates is already there. Only one other thing, If your using petroleum based 2 cycle oil to break in your motor how do you honestly know when it is broken in without really testing compression, heat temps, and consistant rpm's during and after each and every tank of fuel. Now if your engine was actually seated nicely at say 3 gallons of fuel and you have already put through 10 gallons you inadvertently have put 7 gallons of excessive wear through your motor and lessened the life of your rings because they just stretch out to meet piston walls.If you would have used synthetic from the start the break in procedure might have taken 4 or 5 gallons but once the surface was smooth and rings were seated the full protectiong of the synthetic would already be there,in turn taking the guessing factor completely away and fully protecting the engine immediately when it was ready instead of when you were ready.

This is my thoughts on synthetic oil being used for break in.Not the only way!! but one that I have used to much much success.


TerryF