Fundy

Hi everyone,
I'm new to glow engines and I have a 4 stroke .91 Magnum that my Uncle helped me break in. I've asked several people what I need to do to maintain this engine and gotten several responses. I know that when you get done running your engine you're suppose to unplug the hose to the carb and run the remaining gas out of it, but after that - I'm confused. One opinion was to DEFINETLY run after-run oil because the fuel I use (15% 2stroke) has a chemical in it that contains water(I guess?) and that can lead to rust. Then another source told me to not do anything to the engine until the next time you fly it - unless you're planning on not using it for 3+ months. Which school of thought should I go with?

smokingcrater

ask the same question to 10 people, you will get at least 12 answers, all of which are 100% correct! anyway, my opinion... run the fuel out of course, and if you are planning on storing it months, pull out the glow plug and dump some afterrun oil in. (auto trans fluid works great)

Don M.

My Feedback: (5)

Your going to get a lot of different answers to this. I find that if I have a question about a certain aspect of the hobby I look for the guy who seems to have that item down pat. In other words if it's an engine question who has an engine the same as mine that works well all the time, the same with radios, flying manuvers, etc, etc. Then I don't ask anyone else until I decide his way is not for me.

That being said, here's my after run procedure and it works extremely well for me. I bought a gallon of 0% nitro fuel (F.A.I) added a bunch of Castor oil (I use Castor as a storage oil only, but that's another story) - it's probably about 30% oil now. At the end of the day I empty my tank and squit in 2 - 4 ozs. (depending on size of engine) of this fuel, start her up and let it run dry. Unlike a lot of answers you'll get, I won't tell you this is the only way to go, but I will tell you it works spades for me. I average 500 - 600 flights on an engine before I have to tear it down and I run both 4 & 2-strokes.

Hobbsy

My Feedback: (102)

I only use Corrosion X that I get from Sheldons, since I now have 112 engines, some are stored for long periods of time. If I pull a backplate off of an engine after being stored for two to five years, the Corrosion X looks exactly like it did when applied and the inside of the engine looks as when new. I shoot it down the carb on two strokes and in the vebnt tube on four strokes. It foams up for a few seconds an coates everything inside the engine and then turns into a yellowish green liquid. A 16 oz aerosol can lasts approximately a year.

Fundy

Thanks for the responses everyone. I does sound like there are alot of opinions out there. One old timer told me that he'll never use after-run oil again because it clogged up one of his engines. Anyway, since I'm lazy - I think I'll just leave it alone unless I store it for a while. I'm planning on flying pretty frequently so it should work out.
Thanks again.

jessiej

After run oil is cheap, easy to use and won't "clog your engine". There is nothing to loose by using it, but risk of damage by omitting it. A few cents and a few seconds of time change the odds.

IT IS IMPORTANT WITH A 4 STROKE TO SQUIRT OIL INTO THE NIPPLE WHERE USED OIL ESCAPES. Oil inserted through the carb or glow plug in a 4 stroke will not reach the crankcase. Lots of expensive stuff in the crankcase.

There are dozens of satisfactory oils, all cheaper (much) than the hobby shop stuff. Do a search for after run oil.

You will find ardent supporters of many oils. All will do the job.

Sport_Pilot

Yes Jessie get all excited when someone says they won't take the time to squirt some worthless afterrun oil in their engine.

Ernie Misner

A bit cheaper than Corrosion X (but the resultant corrosion inhibiting properties may only last one lifetime instead of three....:-) is a can of 2 stroke outboard motor fogging oil (storage oil). I paid $2.99 for an aersol can of CRC storage oil at the marina. Like corrosion X, the aersol can makes it super easy to squirt up into the crankcase.

Ernie

Blackie

Fundy, I've seen this very question asked many times here on RCU and other forums as a matter of fact I was asking this very same question myself 5 years ago. This is nothing to worry yourself about but I would strongly suggest that you heed the advice from those that say to use the after run oil.

I'm supprised out of the above responses that no one mentioned air tool oil. This is what I use and also by many others, keep it cheap and simple. Just fill the carb barrel on the 46FX then turn the engine over several times.

Blackie

yard-dart

My Feedback: (35)

Fundy,

Go with your insitincts, and my thought also, and forget about the after-run oil. It is only needed if you're going to be storing an engine for any significant period of time. Out of all the engines I have/have had, none of them ever had a corrosion or seizing problem. I think it's simply another way for someone to make money. When you do get ready to store an engine, do as someone else mentioned, use transmission fluid. If I'm out, I use 3 in 1 oil. If you run the engine at least on a semi regular basis, no after run lube is needed.

John

jessiej

Naw, Sport. I ain't been excited since the first time I got hit in Vietnam and I sure ain't gonna get excited over someone else's engine. At least I don't THINK Hell has frozen over yet.

BTW I do encourage folks not to use worthless after run oil though. There are better brands. It is, however, their call.

jess

William Robison

My Feedback: (3)

Air tool oil is great, but my choice is ATF, Dexron II. It's inexpensive and does a good job. It is a "Moisture Displacing Lube," so it lifts any condensation off the internal parts and protects everything. Brand is not important, to get the Dexron II rating they all have to be essentially the same.

Cheap? Eighty-seven cents a quart in the "Auto" shelves at your local grocery store.

Does it really help? I think it does, but regardless what harm can it do? A fraction of a cent per application and 30 seconds to do it.

Bill.

Motorboy

Each time after i ran engine, i give it afterun as i has mixed self 9 parts kerosene anfd 1 part motoroil. It make easier start engine next time.

Jens Eirik

Sport_Pilot

Some day I would like to test it, but I do think that people who use after run oil right after the last run seem to have more problems than those who either don't use after run oil or wait a while. My theory is that since oil is lighter than water that it sits on top of any moisture and traps it. The metal under the moisture then corrodes. If you run out the fuel you expel most of the moisture, the remaining moisture is mixed in the remaining fuel and oil. If you wait for say an hour or so much of that moisture also evaporates with the remaining fuel. If you have castor oil or a mix of synthetic or castor oil the remaining oil will protect it better than the after run oil. At least for several months or more, after that the oil may drain away from the metal exposing it to atmospheric rusting, thus the need for after run oil during storage.

William Robison

My Feedback: (3)

Hugh:

My way:

Two stroke: After engine shut down from the last flight of the day, pump the remaining fuel from the tank. Reconnect the fuel lines, apply glow heat with the engine at proper throttle position for starting, and start the engine. Nurse it, keep it running as long as you can. This gets the remaining fuel out. Disconnect glow heat, go to full throttle, dump a slug of ATF down the intake, and spin the engine for ten seconds or so with the starter. Close the throttle, turn the radio off. Clean up, pack up, and go home. Or have a bull session, or whatever.

Four stroke: After engine shut down from the last flight of the day, pump the remaining fuel from the tank. Reconnect the fuel lines, apply glow heat with the engine at proper throttle position for starting, and start the engine. Nurse it, keep it running as long as you can. This gets the remaining fuel out. Disconnect glow heat, leave throttle shut, pull the plug and put a few drops of oil in the plug hole. Stick the crankcase vent hose into your oil bottle and turn the crank, using the crankcase vacuum to pull a couple slugs of oil into the engine. You can see it go up the hose. Now spin the engine for ten seconds or so with the starter. Put the plug back in, close the throttle, turn the radio off. Clean up, pack up, and go home. Or have a bull session, or whatever.

The two stroke just takes a few seconds. The 4s engine takes a little longer, but since the crankcase of all 4s engines but YS gets no lube beyond the stale and contaminated gases leaking past the piston and ring I think it's even more important on a 4s than a 2s engine.

Concerning your comment on the remaining moisture, the Dexron oils are moisture displacing oils, rather than covering the water they actually lift the water OFF the metal, giving good protection.

Bill.

Sport_Pilot

All oils are water displacing, that is if the metal has a film of oil the water bead on top of it. To say an oils is water displacing is mostly a marketing gimmic, even crude oil is water displacing, though some oils create a better film than others. But it won's stay that way forever, the water is heavier and even will mix with a small amout of oil, so the oil slowly dispersers in the beads until the water is in contact with the metal. With enough oil disolved in the water the water may become a poor eletrolyte, but that depends on the ratio of oil VS water and the size of the water beads. For example water on the bottom of your oil pan eventually disolves with the oil and becomes the thick black sludge in the bottom of your pan. But most cars have the advantage of being run often enough that the water is mechanically mixed with the oil. Long term strorage of water and oil is not a good thing.

Flyboy Dave

My Feedback: (21)

I've never used an after run oil. The castor in the fuel will coat and protect
the internals. In very humid areas the corrosion problem could be much
greater, and extra care may be needed. I service my 4 strokes now and
then with fresh oil on the rockers and cams. The main bearings seem to be
holding up OK, and as long as there is plenty of oil coming out of the crankcase
breather, I'm not going to worry about it. The oil coming out of the breather
is of course....castor.

Dave.

Kmot

My Feedback: (24)

I always use after run oil in both 2 stroke and 4 stroke engines I own. I have engines that I last ran 25 years ago and recently pulled them out of the plastic baggies and they are as clean and beautiful as when I packed them away. I have several car nitro engines that I have been running for the past 3 years and I always do the same procedure. Run then engine till it runs out of fuel. Pull the glow plug, put 10 drops of my after run oil in and replace the glow plug and turn it over by hand a few revolutions. On car engines that's all I usually do because the air filters are usually coated with dirt and crud from running off road. Airplane engines I also added an additional 10 drops through the carb.

It may be unnecessary. Howver I have never had an engine rust up inside. Also, it's a Zen thing. Ying and Yang. It just makes me happy to pamper and take extra special care of the things that provide me with happiness in my life.

Kmot

My Feedback: (24)

Forgot to mention that my after run oil is a blend of Marvel Mystery oil, torque oil, and motor oil.

William Robison

My Feedback: (3)

Sporty Hugh:

Comparing an air cooled mist lubricated aero engine and a water cooled pressure lubed car engine is apples and oranges.

The car has a sump where the lubricating oil is stored, and it does become contaminated by moisture and acids from piston blow-by, as well as plain water from condensation. Included in the oil are detergent additives that keep the moisture in suspension, and ensure the little bits of metal from wear are drained with the oil and filter change. As well as neutralizing the acids. If you make a point of always getting the engine fully warmed every time you drive, 99% of the water and acids go out the breather system, and the oil change interval can be extended with no ill effect on the engine or its life, since you are not accumulating these contaminants. If you run mostly around town, or you live in a cold climate, the oil and filter need changing more often.

Then comes the aero engine. It runs much hotter overall, and it has no sump to accumulate contaminants. But it still gets the acids and water from piston blow-by (Talking 4s here) along with the oil for lubrication. Because of the higher temperture there will never be any amount of moisture inside when the engine is shut down, but there will be some, along with some nitric acid, and a few other contaminants. If the engine is left as-is, with residual fuel in it, the alcohol will also draw more moisture in.

So, whether you use an after run oil or not, at least run the engine until all the fuel is exhausted.

You don't seem to know what a "Moisture displacing" oil is. Granted, if you have a bearing with oil on it, any oil added is added oil. But if you put a water drop on dry metal, and then put a true MDL on it, the molecular action of the MDL will actually lift the water away from the metal, and give it a coating of oil under the water.

Try an experiment. Thoroughly wash three bearings, junk ones please, get all the oil off them. Lay out a sheet of plastic (or similar) that you can leave for a week or two. This will be more "Real world" if you have some nitric acid, but ordinary mild acetic acid (vinegar) will give you the idea. Tie strings on your bearings so you can dip them. Take the first one, dip it in the acid and just put it on the plastic. Dip the second one in the acid, and then into freah automatic transmission fluid, Dexron II, and set it on the plastic. For a control, dip the third clean bearing into the ATF without first dipping it in the acid. The first, acid dipped without oil, will start rusting almost immediately. The acid/ATF bearing and the ATF only bearing will last two to three weeks before starting to rust, and will start rusting at almost exactly the same time. Thus proving the moisture displacement, and neutralizing the acid.

Bill.

Sport_Pilot

No it doen't prove any such. Acid doen't cause rust. You can etch metal with acid and no rust. Have you seen a car stripped of paint and lightened by thinning the metal with the acid? The car is then diped into another vat to neutrilize the acid and when removed the car is stripped and much metal removed with no rust. However, when exposed to air it will rust in short order if not spayed with oil or paint right away. Acid is a very effective electrolyte. To rust you need an electric current and oxygen, the acid provides the conductor to generate the electic current. If you dip steel and a gold rod into a good electrolyte, could be acid or salt water, you will measure a voltage across the rods. The voltage will vary with the rod elements used. The differance in the number of electrons in the atom between the two metal elements determines the voltage. Therefore steel and copper will have a fairly low voltage, and gold and zinc will have a higher voltage. The less nobel metal, the one with less electons will corrode if oxygen is present in the electrolyte. This is known as a galvanic cell. It should be noted that a crankcase full of water will make a fairly good galvanic cell, but it would be the aluminum that would suffer the most. However a mist of moisture would be a differant sort of thing.

The ATF fluid is simply creating a barrier to prevent oxygen from getting to the steel, since oxygen is present in the acid, it will still rust, it just takes longer and is not as severe. To say the oil has high water displacement basically means it coats well, and doesn't strip away in the presence of water. All mineral oils and most vegatable oils have this property, just some are better than others. It doesn't mean that it magically push's water aside, but if the metal is already coated with the oil it will prevent water from touching the metal, for a fairly long time.

Another point, nitric acid is very unstable. Pure nitic acid will decompose and may even explode if exposed to air, it is a very good rocket fuel. Any damage from nitric acid is immediate, it does not stay around long enough to cause rust during storage. However, nitro itself is a mild acid.

There is another acid which occures with any combustion of hydro carbon's, and I suspect with alcohol to a lesser extent. The name of the acid doesn't come to mind, but it is the one that you mentioned accumulates in a car engine.

William Robison

My Feedback: (3)

Hugh:

The most common acid formed in an IC engine, whether gasoline (Hydrocarbon) fueled or alcohol (carbohydrate) is nitric. Gasoline: HC + O + N = H20 + CO2 + HNO3. I know the equation is not balanced, its just to show what goes in and what comes out. Alcohol: HCO + O + N = H20 + CO2 + HNO3. Essentially the same thing. Contaminants and additives in the fuel, and oil leaking into the combustion chamber will result in traces of other acids, sulphuroc and carbonic for two. But water and CO(x) are the primary components, with nitric acid coming next.

Both these examples, of course, are conventional engines. When we have the lubricant mixed with the fuel we have a much more complicated soup, and several other products are formed. But still, water, carbon dioxide/monoxide, and nitric acid are the main parts of the exhaust.

When nitric acid breaks down, depending on what the reactant is, it can do anything from turning into water and gassing nitrogen off, to making steel or iron rust.

Okay, so "Neutralizing the acid" was a poor choice of words, I should have said "preventing the acid damage to the metal." But there are buffers in ATF to maintain a neutral Ph. And this does neutralize the acid.

And reading through your post, you have admitted the oil does, if not prevent the damage, slow it down. For the almost free price, I'll take what it gives me.

Bill.

Boomstriker

It depends on what type of fuel you burn and how long you go between flying.
If you use a Caster or Caster blend, you better use after-run oil if it's going to sit for any time.
Caster does not protect against rust without the after-run oil.

If you use the synthetic oil fuel like Cool Power or Wild Cat, which specify that after-runs aren't required, the engine will stay clean and shiny inside and out without the varnish and gummy build-up that Caster leaves.

Kirk

Rodney

Boomstriker, someone has given you some bad information.

Sport_Pilot

It's castor not caster!