View Full Version : Mixing Synthetic and Castor Oil fuels in your airplane?
08-02-2003, 10:25 PM
Do you do this? If so, in what ratio? Do you run 2 stroke or 4 stroke?
I have a new jug of synth and thinking of mixing in my remaining castor jug (around 1/6th left).
08-02-2003, 10:35 PM
No problems - all the model engine oils are made to mix with alcohol based fuels and are fine to mix together.
I mix them all the time.
I usaully mix about 80/20 synth to castor. Sometimes I go as high as 50/50.
If you use the 80/20 you can run most engines safely on 16 to 20% oil content. IF YOU"RE CAREFUL NOT TO GET TOO LEAN. I often mix 18 to 20 % just for a safety margin!
Ok, I'm tired, I read that wrong. :oops:
The answer is "Yes"
08-02-2003, 11:39 PM
You just wanted to get 2 posts in for the price of 1 ! :wink:
Jim Moss :)
08-03-2003, 05:25 AM
No problem mixing the fuels as far as compatibility however I would hesitate in doing that as there is more possibility that the closer to the bottom of the jug the greater the chance that contamination has made its way into the remaining fuel. Why not just use one up then switch to the newer jug. That way if the first one is contaminated you will not contaminate both.
08-03-2003, 07:08 AM
A few years back I use to do do this with all my fuel. I would put 2 ounces of bean oil into a full (new) gallon of Cool Power 15% 2 stroke fuel to give it a little extra oil content. I found that it would make the plane smoke a little more but it didn't load up the plug or have any real down side to it. For the last 4-5 yrs I stopped putting the oil into the fuel . I've found the Cool Power 15% 2 stroke fuel to have enough oil content in it for all my 4 strokes.
08-03-2003, 12:33 PM
After rereading your post I see that I misinterpreted what you were asking. :oops: I think propworn hit the nail on the head with not introducing old fuel to a new jug. Contaminated fuel can give you all sorts of different problems......
08-03-2003, 04:01 PM
I wouldnt be worried. As long as the fuel has been capped and is still good. Dont assume that a partially used jug of fuel is "contaminated" - heck we would throw out more than we would use!
I oftem use partially empty jugs. Mix them and so forth, but I allways use a filter and never put fuel back into the jug. And never take the cap off except for the inital placing into my flight box, and maybe once more when I refill from a new jug.
08-03-2003, 08:38 PM
How does one get several partial jugs of fuel??? Why would you open a fresh one before finishing the last one?? Properly stored fuel has quite a long shelf life. I have never had a jug of fuel even near the end go bad on me. When I open a new jug of fuel I put the sullivan aluminum cap on it and it has a nice oring and once the ends of the hoses are capped it is as sealed as with the original plug and screw on cap. I use one fuel for all my engines and there is never any reason to open a new jug till all the fuel in the old is used up.
08-03-2003, 08:49 PM
I wouldn't mix an old questionable jug with a new jug.
Simply put ... I am almost out of my Caster jug and bought a new jug of Synth to try it on a newer engine. I have read about mixing, and thought of doing it but wanted to get some input first.
Another question ... I have an older engine that has always ran on Caster. Can I run Synth through it now or am I committed to Caster on this engine? It is a late 80's Irvine .61. First time I fired it up was around '96 and have been running it each year since. Still runs great, but it has lots of hours on it with a Caster fuel (Omega, 15%).
08-03-2003, 09:02 PM
Come on guys, why assume the 1/6th jug is 10 years old and questionable?
Dennis, often I will use up 1/2 or 3/4 jug of fuel, and becuase my electric pump doesnt like to pull fuel out of the last 1/4, I pop in a new jug into my flight box. When that new jug is down to 3/4 full I pour in the remainder of the last jug. OK?
Like I said - his question was SPECIFICALLY whether or not castor and synthetic based oil fuels can be mixed, nothing more. Why turn it into a discussion of old used up fuel, contaminated, etc...?
To re answer your question Lord Kimbo, YES you can definitely without any problems mix any type of model fuel with any other type. All our fuels are based on methanol, nitromethane, and oil (synth or castor or a mix allready).
All you will do is (a) change the nitro % based on how much of what you are mixing together and (b) change the oil make up and % based upon what % was originally in each jug and how much was synth and castor.
I also mix castor based fuel and 100% synth fuel together in varying nitro contect to tailor the nitro level for particular engines. No problem!
The key is (to repeat myself) KEEP YOUR FUEL CLEAN and FREE OF MOISTURE and you can use it for a long time.
08-03-2003, 09:05 PM
Another question ... I have an older engine that has always ran on Caster. Can I run Synth through it now or am I committed to Caster on this engine?
What type of engine? If its an older lapped steel/iron piston & liner like an older OS, fox, enya, K&B etc you want to run some (if not all) castor oil and in at least 20% or 22%.
Any modern engine (ringed and/or ABC/ABN,etc) can definitely be run on synthetic UNLESS they suggest strongly not to (like the Moki's I wont take a chance).
08-04-2003, 01:54 AM
Andrews, He is right on about the fuels. ZKeep it clean and watch for any sediment on the last bit of fuel. Also have a good filer int he transfer line and one whenpulling it out.
For your ringed engine I would add about 2% of a good grade of caster. This will maybe alleviatte some of th proplems on the older engine.
08-04-2003, 11:11 AM
From my kart and motorcycle racing days the mixing of different oils (synthetic) were not always compatible. I don't know if this has changed but I can remember Klotz telling us to run one oil or another and not to mix them as there was no research done as to whether both oils would remain in solution or not. Any of the other oil companies were likewise concerned about combining their product with someone elses. To be on the safe side we heeded their advice and did not mix.
08-04-2003, 11:19 AM
I buy Sig AA castor oil and mix it into pure syth oil fuel all the time. No problems EVER...
Maybe in extremely high percentages (not that we ever use more than 25% and that is rare) but not in the 16 to 20% ranges.
08-04-2003, 05:27 PM
but I can remember Klotz telling us to run one oil or another and not to mix them as there was no research done as to whether both oils would remain in solution or not. Any of the other oil companies were likewise concerned about combining their product with someone elses. To be on the safe side we heeded their advice and did not mix.
I raced gokarts for a number of years as well Dennis and did lots of mixing.
The only reason they told us not mix them, was so we wouldn't buy the competitions oil. :wink:
Not that we found an advantage to mixing synth. oils though.
Now Oxypropelene in the gas, that was a mix!
Melted many coolers using that stuff (Had to keep it cold) ! :twisted:
Jim Moss :)
08-04-2003, 05:47 PM
Andrew maybe I should clarify what I said. It wasn't meant as a criticism or to be argumentative.
First of all I do not disagree with what you are doing. Since I can safely assume we both go through lots of fuel. I understand that you mix and match but your knowledge base is probably greater than most.
This is where I have a problem with a general statement about mixing fuels.
Most of the guys in our club and I imagine most other clubs do not have secure lids on their fuel bottles. They use those plastic things that can and do leak air around the fittings. Some, their fuel jugs last months not weeks. Some will only go through 2 jugs a year flying both summer and winter. Most do not store their fuel as carefully as we might for prolonged usage. All this can lead to the last bit of fuel being contaminated.
It was not castor that had incompatibility issues but the different synthetics with each other. Like mixing cool power and Red Max for instance. Of course using the same brand of fuel for mixing is the answer.
Bean oil or castor will mix with just about any fuel with compleat compatability.
Castor has given problems with the regulators in some engines but if you are using those you should be following the manufacturers recommendations as to the type and content of the oil.
To me clean, fresh uncontaminated fuel is one of the easy safeguards that anyone can do to help keep their plane out of the dirt. I have seen everything from guys buying used half full fuel at swap meets to using a smaller bottle on their flight box and they just keep refilling it over and over never noticing the build up of crud in the bottom till they start to have problems. These are not beginners either they should know better.
Yes mixing fuels that are known to be fresh and uncontaminated of the same brand to adjust nito content or as Andrew does to help with the fuel pump or adding castor to increase oil content are all acceptable practices.
I use Wildcat pure synthetic only. I contacted them and asked what oil they use. Klotz I was told and I have on hand a container or Klotz pure synthetic as well as the Sig Castor. I will adjust the oil content as needed.
My feeling is that if there is a reason to mix fuels to achieve a certain mixture do so. But the general statement that everything is compatible is a bit misleading to those who do not know any better. I would never mix two different brands better to use one up then switch to the other.
These are my personal practices and they have served me in good stead for the many years I have been racing karts, bikes and flying planes. With the cost of fuel today pouring that last little bit into a new jug is not something I would do so I could not in good conscience recommend it to anyone else.
One thing I have found in this hobby is that there is no one way of doing things. There are so many different ideas out there and yes the majority of them all work. Find a system that works for you and one that you have confidence in and use it.
08-04-2003, 06:11 PM
Jim I have raced for lots of years and I have never heard a reputable oil manufacturer say anything other than we would like you to use our product but use what you feel you have confidence in. I have heard please don't mix ours with anyone elses run one or the other.
In bikes the oil injection system could be adjusted for the viscosity of the engine and the two different oils may be different. In the early days we never trusted these pumps and premixed our oils.
The other concern that was noted by Bellray and Klotz were the possibility of one of the oils or both partially separating or coming out of solution due to a false saturated condition.
If you read the tech info even today some synthetic manufacturers warn about using a 100 to 1 synthetic at higher oil content ratios as the oil may indeed separate. Don't you remember having to shake the old outboard tank if you left it for a long time to remix the oil.
Probably todays technology has all but eliminated many of these concerns but as I said I use a system that has not failed me in 35 years of tinkering with engines so as it is the only why I have knowledge of it is the only one I could recommend.
08-04-2003, 06:44 PM
I maybe forget my chemistry lessons from school, BUT....
the methyl alcohol inour fuel is the base constituent, correct? There for it is the solvent.
The oils the fuel manufacturers use are ALL formulated to mix with alcohol.
If two separate oils are both soluable in methyl alcohol, why in the heck would one of them or both come out of solution when mixed together?
Its like when I mix my rye and ginger, if I add a wee bit of water they all stay in the solution ;)
My point was the guy didnt ask whether or not he should mix some old fuel with some new fuel. He asked a straight question, whether or not castor and synth model fuels can be mixed. I prefer to answer that question with a straight answer - YES. nothing more, nothing less...
08-04-2003, 08:21 PM
Andrew you win. I grant you grand authority on all to do with rc aircraft. I guess your opinion is the only one that counts. Sorry I bothered to try and add something to the mix wont happen again I assure you. Have a nice day. It wasn't a critique of your methoods only someone elses opinion thats all.
08-04-2003, 09:42 PM
08-04-2003, 09:49 PM
Hey, this is my thread ... take it to the chat room... ;)
08-04-2003, 09:55 PM
sorry, I must appologise for any thing I said sounding a bit crabbish. I am having somthing "difficult" to deal with right now and it is affecting my normal happy self... no excuses.
08-04-2003, 09:56 PM
For someone that has over 2000 posts, I think we can let it slide. :) Man that is impressive.
08-04-2003, 10:30 PM
If you want to throw something else in to the fire. I believe also it has a lot to do with the nitro content. FAI3D is straight alcohol and oil(caster) when racing. They supply it on site and watch you empty and fill. F1 is any fuel you want. They use synthetic and also no caster since above about 35% it won't mix with the nitro properly. If anybody has tried mixing it you will know when you see the little blobs in your fuel. Besides if I am selling a synthetic product why should I put something else in it.
On the side note I liked to put a little caster in for the lean runs. Synthetics have a tendancy to burn up at high heat, and some oil is better than none. Who was it a few years ago cheapened out on the oil content and people burned up a lot of engines.
Just a few of my thoughts. I still have a few jugs of 70% stowed away.
08-06-2003, 06:39 AM
I have often heard people say that various oils burn up at high heat. The oil burns in the combustion chamber. By that time it has done all the lubricating it is going to do. So who cares if it burns?
08-06-2003, 08:58 AM
If the oil burns in the combustion chamber what is all that stuff I keep cleaning off my airplane? :wink: :wink:
08-06-2003, 09:18 AM
A quote from the article on castor vs synthetic. The most frequent comment I hear from lovers of all-synthetic fuels is, "Brand XX leaves a lot less oil on my model." My response to that is, "Doesn't that bother you? If you don't see much oil on your model after flying, that tells you one of two things - or both: Either there wasn't enough oil in there in the first place, or the oil is burning off with the methanol. Neither is good. There's no way oil can burn off and properly lubricate at the same time." This is usually met with a puzzled look, then one of the light dawning, having just realized something they never thought of before.
Complete article http://www.rccanada.ca/tech.php?art=fuel2 also, it can be found on RC Canada home page.
08-06-2003, 05:20 PM
If the oil burns in the combustion chamber what is all that stuff I keep cleaning off my airplane?
It is burnt oil!
I do not know that any material disappears completely if you set fire to it. It may change it's state but it will not disappear.
08-06-2003, 05:59 PM
I am getting out of this. :) But it is a good article. I also reccommend emailing: Dave Schadel(Performance Specialties) or Dubb Jet (Jet Engines)
They will give you the information. They don't make all there money from just selling new engines.
Dave gave a 2 day course to us in N.Battleford on racing and engines and it was very enlightening.
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