crashinator

Why do they use synthetic oil?


Because I am lazy and dont want to read ALL zillion pages of awesome knowledge, let me ask this.....if synthetics flash before castor and has poor anti-corrosive properties, what are the benefits of using it?

gkamysz

My Feedback: (19)

Be prepared for your own zillion page thread.

Synthetics burn cleaner, that is the main reason they are used in model fuel. They don't leave varnish residue on the engine. The model is easier to clean. Some synthetics are every bit as good as castor oil. Some castor oils do not varnish or carbon engines either. It's a mixed bag. Do your homework, by reading those zillion pages and make an informed decision. I use both and am happy with both.

Ask the same question about why castor oil isn't used in vehicle crankcases, it is superior right?, and you'll see why.

In the end Castor oil just happens to work pretty darn well in model engines. Maybe even better than highly engineered synthetics. I say maybe because nobody has proven either way.

Sport_Pilot

I don't think anybody has said that castor oil is better than mineral oil used in an automobile. The mineral oil is superior to castor, but it won't mix with methanol and nitro.

Jezmo

In my humble opinion they use it because of the cleanliness. Only they know for sure. I personally use fuel with a blend and I feel that gives the best of both worlds.

OK now I am outta here before the heavyweights get here.

Fuel Dinosaur

Newer synthetic oils are used because they burn clean, with low ash and carbon buildup, they are now relatively inexpensive and can be produced at varying viscosities (thickness), most are fully miscible with methanol, that is they mix completely with methanol, the preferred, inexpensive alcohol for model engines. One example is some of the newer helicopter oils,some are very thin (low viscosity, they flow easy) and can be used at high concentrations with methanol to produce decent lubrication of model helicopter engines. It is not often either OR in model fuels, that is, synthetic oils have properties that castor oil does not and vice versa. I use them both and have for a long time, in competition flying and in sport flying, cars and boats. Castor oil is a natural product and is made from the pressing of castor beans and is not processed very much. It has a high film strength and sticks to the piston, ring if you have one, and certainly the lower connecting rod to crankshaft region and the bearings or bushings. Castor oil also forms chains, called polymers, that help a 2-stroke engine protect itself from a very lean, fast run. They also build up on the top of the piston as a black residue. Believe it or not, castor oil does provide decent protection against rust long term. SIG Champion 2-stroke fuels contain 20% oil total, of which half is castor and the other half is synthetic. Kind of gooey, but provides great protection for your engine. Some modelers prefer all synthetic oil for their 4-strokes. I personally use 2% castor in my Saito 4-strokes, 18% total oil, but use 3.6% castor in the summer when the temperatures are in the 90s or higher. Not much of a problem with 15% nitro and these engines run nice and cool. In summary, there are advantages AND disadvantages to synthetics and castor. Many current suppliers of model fuels have reduced the oil content in their offerings. My sense is that few engines have ever been ruined by running 18% or even 20% oil in them, but I have seen pistons burn holes in the top in competition when extremely low levels of oil were used. Hope this information helps. Enjoy your flying! The old fuel mixing dinosaur.

XJet

If that's true, why do synthetic motor oils perform better than mineral-oils?

Think about it... if mineral oil is better than castor and synthetic is better than mineral oil then it stands to reason (by your logic) that synthetic is better than castor by a significant margin right?

XJet

I see no reason why the cause of the piston-burn would be due to low-oil ratios.

gkamysz

My Feedback: (19)

I was wondering who would pick up on that.

Motorboy

Think winter!!! The syntetic oil will come first to all moving parts before mineral oil and castoroil if the oils was used in the automobile engine. But the oil film in castor oil can not break down easy as syntetic oil can do it..

Castor oil can not be used in the automobile car since the oil will be rancided (gummed oil with other word) with time.

See this article: http://www.modelenginenews.org/faq/index.html#qa5

Sport_Pilot

Synthetic oils in the automobile industry are indeed superior to mineral oils, but they don't mix with alcohol! We cannot use that oil nor automotive synthetic oil. The synthetic oil's we use and even the castor oil is inferior to automotive mineral oil when used in the crankcase. The synthetic brake fluid used in automobiles are made of the same stuff as our synthetic oils, because it will work better if some moisture gets into the system. But your automobile engine will burn up big time with that! In fact the fact it is inferior is one reason we must put more oil in our fuel than the gassers! That and a few other things.

Sport_Pilot

It can be used and was used at one time, but must be changed often. It was better than the early mineral oils, but way too thick for modern engines and thins out with heat more than mineral oil.

XJet

Well there are three major families of synthetic oils. PAO (Poly Alfa Olefins), PAG (Poly Alkylene Glycol) and Esters/DiEsters.

Most PAGs and Esters *will* mix with alcohol but PAOs won't.

Many automotive synthetics are PAO so they won't mix with alcohol.

However, many of the higher-quality automotive oils are a PAO/Ester blend, the ester seemingly providing a valuable increase in VI (viscosity index) and other benefits.

The inference of your statement (quoted above) is that our model synthetics are somehow inferior to the automotive synthetics which is only sometimes true.

Yes, the cheap PAG oils used by most of the US model-fuel industry may be inferior to the synthetics used to make motor oil but the higher-quality esters used by the likes of Motul, Aerosave/synth and Coopers would appear to actually be superior in many ways to the PAOs found in the sump of many cars.

I see lots of people in the USA decrying the use of synthetics and pushing castor - but how much of that is simply because they're using a second-rate synthetic?

I still can't understand why people would want to waste so much of an engine's power by using it as an oil-pump, by requiring nearly 20% of the fuel to be some low-performance synthetic especially when you can go to 10% oil if you use the right stuff.

In my own experience, by going to 10% you get significantly more run-time per gallon of fuel (saves $), more power, better transition and (gasp!) *cooler* running.

Why are so many people living in the past?

Sport_Pilot

Unfortunately that usually the only synthetic available. The good ones seem limited to the overseas market and possibly Coopers.

Because we are forced too? Where do you buy this fine oil, how much is it, and what are the health hazards?

XJet

Well I buy Coopers direct from CooperFuels.

It's actually biodegradable and non-toxic so the only real health hazard is if a case of it falls a great distance onto your head I suspect :-)

Now that we're running 10%-12% (depending on the blend) it's saving us a *fortune* when compared to the older oils that CoolPower and Klotz use.

Not only are we using around half the amount of oil per gallon of fuel but since a gallon of fuel seems to go a lot further, the cost per flight is way-down.

With the rising price of all fuels, this is a big bonus on its own.

gkamysz

My Feedback: (19)

The ester based oils are biodegradable. As Bruce says Coopers has theirs for about $36 a gallon plus shipping. I've not tried it yet. There is also Motul Micro, which is quite expensive. http://www.performanceoilstore.com/products.asp?id=9 $40 for 2 liters.

The other point is that if Castor is so good why not run it at 10-12%?

Red B.

Touché!

Sport_Pilot

If its not an old iron piston type, I think you can, but not much reserve for a lean run. I probably would try Coopers at normal percentages at first, then maybe 15% for a long while. But I have both Castor and normal synthetic to get rid of first, and since I haven't flown anything in about 9 or 10 months, [] its going to take a while to use up.[&:]

XJet

That's exactly what I did.

Started at 16%, went down to 14% and now I run 10% or 12% depending on the engine and nitro percentages.

My old(est) TT46Pro now has about 450 hours running (most of it on Coopers at either 12% or 14%) and it's still going really strong, hauling a 4.5lb profile around like a ragdoll and providing very good pull-out of a hover with just 5% nitro.

I'm just about to switch to Coopers in my DL50 too.

liquid_TR

So then is it a viable option to go from 17% total oil 30%-70% castor-synthetic mix, down to 14% total oil 50%-50% castor-synthetic mix? my synth is klotz KL200

XJet

I wouldn't not if your oil is Klotz, it's a fine oil when used in reasonable percentages but I don't think I'd want to run it at the same lower ratios that the more advanced oils will allow.

An interesting story from last week...

I gave a friend (who flies helis) a quart of Cooper's oil so he could mix up some fuel. He mixed up a blend of 10% oil, 20% nitro and 70% methanol.

A couple of days later I got a phone call.

"I had to land my helicopter today for a very unusual reason" he said.

"Why" I queried, hoping it wasn't bad news.

"I got tired of flying. A tank of fuel lasts so much longer than it did before" he explained. "Usually I have to land because I'm low on fuel but this thing runs forever on a tank now"

Needless to say, he's demanding I get him some more oil he's hooked :-)

The combined saving of being able to use less oil and have expensive hi-nitro fuel go a lot further means he's cut his flying costs considerably.

Sport_Pilot

Klotz is more of that brake fluid we spoke of earlier. Not much thicker either. You would be better off reducing castor oil to those percentages. Klotz is about as thin as 5W to 10W oil at room temperature, castor about 50W.

balsaeater

Do you know what number the W is for the ester based oils like coopers or EDL ???

Balsaeater

gkamysz

My Feedback: (19)

I'm not sure what you mean by this. Typical Castor is SAE 50 rated, not 50W. That means according to the SAE J300 specification it has a viscosity of 16.3-21.9cSt at 100°C. 10W-30 engine oil is rated 10W (7000cSt at -25°C). This si a completely different rating. It doesn't matter that the low temperature viscosity of synthetic oils is smaller than that of other oils. The engine runs at 100-150°C. Most synthetic oils will have a lower room temperature viscosity than castor or mineral oil. This is what defines their high viscosity index. A high viscosity index means that it will also not thin out as much above 100°C. Few oils can have a viscosity lower than Castor's ~18cSt at 100°C and still have a higher viscosity than Castor at 150°C. The oils that Bruce talks about have this characteristic. Do not judge an oil by it's room temperature viscosity, unless you fly in the winter and you like to hand start. In that case you should be looking for the oil with the least viscosity at room temp, that still gives has the proper viscosity at operating temperatures. That would be the Ester based synthetics. Since most of us don't fly at -40°C that rating is useless.

Sport_Pilot

I was estimating the oils viscosity, I did not mean that I knew their exact viscosity's. But I have read that the normal synthetics are still much lower than castor oil at operating temperatures.

gkamysz

My Feedback: (19)

Oil viscosity at temperature is easy to figure out. Look at the spec sheet for Klotz Benol and look at the spec sheet for their synthetic lubes. You will find that they are very similar at operating temperature of 100°C. Oils are not normally rated above 100°C and that's where knowing the viscosity index lets you figure out what it will be at 150°C. But we have to realize that viscosity is not the only thing influencing lubrication. Ester based lubricants are "clingy" and adhere to metal very well.