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Fuels Paradise

fuel choice commentary and chat

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Ted Day13/02/2008 17:35:00
11 forum posts

Can someone help me, please.  I am a returnee to model aircraft and have built a trainer, from plans, and it has been flown by a fellow club member, very successfully I might add.  The fuel I purchased is, Model Technics molecular blended fuel, GX-5, and the engine runs very well on it, I have run about six tanks of fuel though it.  When I turned up at the field and club members saw the fuel I was intending to use, I was given advise ranging from, 'use it to light your BBQ, but don't put through that engine', to , 'I would only use that stuff to clean my bicycle chain'.  

My question is, what is wrong with this fuel? if anything, and does anyone know the make up of the fuel?.  Is it castor or synthetic, and does it contain nitromethane?.

Confused Ted 

Myron Beaumont13/02/2008 19:15:00
5797 forum posts
51 photos
I use it all the time for my 2 & 4 st . Funny you talk about what people say .Let me give you an example -(at the geordie nats) I was talking about props & an "expert " said that the ones that I used were only fit for stirring paint with .I still use those black ones for sport flying and wouldn't use anything else & by the way I've never had to balance one ever  ! I have heard that one should only use a synthetic mix   10 % nitro & forget the rest of the products on the market 'cos they contain castor oil ! !! who do you believe Eh!
flytilbroke13/02/2008 20:45:00
2083 forum posts
5 photos

If it works don't "fix" it. There is an awful lot of opinion out there regarding fuel. Strange, as what is opined to be useless is used by many modelers over quite a few years, successfuly.

Use your GX-5 and have fun.

Malcolm Fisher13/02/2008 21:13:00
641 forum posts
7 photos

I have no objection to synthetic oils, but am most concerned about the use of castor. When I started using model engines in the 1950s, diesels not glow, all fuel was castor based, and I suppose I have been indoctrinated by this.

A couple of years ago one of my sons very generously bought a Wankel as a Christmas present for me.

 The instructions said to run in on a high castor oil content fuel and then use a a fuel containing a minimum of, I think, 25% castor - I can check as I still have the instruction sheet but it's in my "hangar" at the end of the garden.

 Where does that place me in terms of Steve Dorling's article when he says "follow the manufacrurer's instructions" yet at the same time advocates never using castor oil?

Eric Bray13/02/2008 23:32:00
6600 forum posts
2 photos

Castor oil is a natural product, for a start!

Yes, us 'oldies' used castor as a lubricant for our engines, and so does most of the racing fraternity, whether car or bike is irrelevant. All the first War aircraft used castor too, and it was a standing joke that there were no constipated single-engine pilots!

When synthetics first appeared, we were all advised to avoid the stuff like the plague, because it didn't lubricate, it just formed a glaze, then the engine siezed! 

I've not flown infernal combustion models for years, now, but castor USED to have a wider temperature range than synthetic, before the engine began to complain, so you could get away with a lean run if you used castor, but not synthetic. Perhaps that has changed now, i wouldn't know.

The same is happening with electric flight ie, don't use lipo's, they spontaneously catch fire, but nicads are too heavy! etc, etc.  

I do recall that the OS Wankel was a very oil-hungry engine, - and congrats on possessing one, they are like platinum hen's teeth. 

Malcolm Fisher15/02/2008 17:32:00
641 forum posts
7 photos
Thanks for your comments Eric, but you haven't solved my dilemma. OS says use castor based fuel, most modern gurus including Steve Dorling and Brian Winch are totally against castor yet both have said "do what the manufacturer says"...
flytilbroke15/02/2008 22:07:00
2083 forum posts
5 photos

I think only you can solve that. The argument for castor or synthetic or even mixed has been going for quite a few years. I can say I have gone all synthetic base fuel with no problems, indeed as I do not now have sticky or gummy residue I am pleased. From what I gather the majority of Alchohol based fuel users are now using synthetic. To make matters worse one Manufacturer specified one type or did, while the main distributer said they would only cover waranty when the other was used.

LHR Dave16/02/2008 18:48:00
131 forum posts
37 photos

I have used this fuel since i began to fly my trainer which is about two years.I have had no problems at all with it only that it does seem to leave alot of  thick oily residue all over my model.I will try a different brand when this current batch runs out and i will let you know how i get on.

Malcolm Fisher16/02/2008 19:52:00
641 forum posts
7 photos
LHR Dave, It sounds as though you are using a castor oil fuel, but you haven't said. I have used mostly castor oil in my fuels but have also used synthetics and even multigrade oils as used in motor cars when I mixed my own brews. As far as commercial fuel is concerned, I usually use Model Technics as stocked at "my" local model shop.
Chris Channon16/02/2008 20:32:00
57 forum posts
1 photos

Malcolm, i would suggest you ignore what you read from Mr Dorling  and continue with using the fuel you have, it will be fine, i bet Mr Dorling has engines that are over 25 years old ( i know because he has said so ) that have been run on nothing but Castor based fuels and are still running well, surely, what is good for Mr Dorling is good enough for the rest of us?

I am not, having a go at Mr Dorling, i just get really fed up with people saying now ( after years of use with no problems) that castor based fuel is a no no,

Surely if it is ok with Saito, OS, SC, then it must be ok to use for the average modeller?

I have just this week bought an OS .70 instructions suggest at least 15% castor

Super Custom 1.60 instuctions suggest at least 10% castor

Saito .56,  not sure on this one, instructions say no castor, Mcgreggor say at least 10% !!

Use castor and enjoy a long engine life!!

Chris C

Malcolm Fisher16/02/2008 21:10:00
641 forum posts
7 photos

Chris, I have engines (diesels) which date back to the 1960s, have never had anything but fuel containing castor oil and still run as well as I can remember them doing - my grey cells are getting a bit tired. Some are, admittedly, a little more difficult to start than they used to be and most seem to like a tad more compression until they warm up. A few have been treated to a brew which used rape seed oil and no ether which seemed to give more power but were more difficullt to start needing a prime of ether content juice to start with.

My glow engines have always been run on straight fuel, sometimes with synthetic oil. I do have fuel with 5% Nitro because that was what OS recommended for the Wankel with a higher than my normal content of castor oil.

 I rarely have problems with engines cutting out or "going sick" except when I underestimate the length of time I've been flying and run out of fuel.

My initial post was, somewhat "tongue in cheek" as I really  have no worries about using castor based fuel and wanted to point out the diuscrepancy of manufacturer's advice versus "engine guru". I might change should I ever buy a new engine the manufacturer of which says "avoid castor oil" - unlikely at my age as I'm sure that those I have will see me out...

Brian Clancy23/06/2008 11:57:00
13 forum posts


 As a relative 'newbie' to the hobby I was a little confused about fuel selection myself, so I spent a little time looking into the subject and avoided the masses of conflicting 'advice'. I made a list of the qualitys I was looking for in the fuel from price and availabilty to engine manafacturers recomendations. I looked into both castor and synthetic based lubes and as an engineer have some knowledge of oils, finding plus points for both!

I decided in the end to go for Model Technics 'Formula Irvine' fuel. Its synthetic based oil component contains 20% castor imparting some of the qualitys of castor into a lube with all the advantages of a fully synthetic. It meets all my needs, its recomended by both O.S. and Irvine, runs very cleanly, engines start very well and throttle nicely with plenty of power even on a 5% nitro mix. I  use it on my Irvine 53 and my big Super Custom 1.20 four stroke. Both engines have been stripped and checked after some hours of running, finding no nasty 'gum' or tarnish and very nicely bedded in surfaces. There is none of usual 'toffee tarnish' on the exterior either!

Well thats my humble contribution, for what its worth, but at the end of the day its a personal thing and I reckon may well be an argument that will run forever!

 Hope it helps


Malcolm Fisher23/06/2008 12:57:00
641 forum posts
7 photos


You don't say what the total oil content of the fuel is, but I would guess that the castor will only be 1 or 2% of the total volume.

 Most of my model engines have been run on "straight" fuel with the exception of my Wankel and ASP 52 four stroke which both suggest having 5% nitro, and I believe in following the maker's instructions.

 My original post on this thread was probably a bit "tongue in cheek" and aimed at those who dislike castor while at the same time saying "follow the maker's instructions".

OS say to run in the Wankel on 25% castor and thereafter to use at least 20% castor. Who am I to disregard this.

Brian Clancy23/06/2008 13:11:00
13 forum posts

Hi Malcolm

 The total oil content is 18% so your about right. I have to say I think your right to follow O.S. recomendations, after all, it IS thier engine and they really should know best! All in all, I have to say myself that either oil type should be fine, its probably more important to stress that good mechanical sympathy (I.E. propper running in, allowing an engine to warm up a little before before putting it under load, correct mixture and good cooling and cleaning) are way more important to the life span / perfomance and reliability of an engine than the exact type of oil / fuel you use!

Jonathan Brooks23/06/2008 13:38:00
67 forum posts

Good quality brand fuel is the way forward.

Synthetic lubrication is now so good it is better than castor. Steve Dorling, in his defense, quite rightly suggests that castor will eventually bugger up your lovely four stroke as it will clog the head, tappets etc. 2 stroke less of a problem except for the inevitable brown grunge that looks terrible and causes sticky throttles and barrels.

Have a hot run with castor and you also have the probelm of the lovely hard brown coating all over the ball races which then stick - - more problems.

The biggest problem/caveat, is too make sure that you have enough oil -castor or synthetic in your fuel for the appropriatye engine. Check the manufacturers destructions and make sure your oil content complies or you can kiss any warranty goodbye.

If synthetic is good enough for Mr Rossi and Mr Hamilton then its okay by me. But I heed all the warnings and wouldnt buy synthetic that wasnt by a reputable manufacturer (with a name to protect).

Castor is obviously fine as it works and some engines have lasted along time (probably as much to do with careful operation and maintenance) but a good synthetic lubricant has advantages.

 Fully expecting to get shot down for these comments but as moved to 2.4ghz give it your best tranny switch on.

Brian Clancy23/06/2008 14:30:00
13 forum posts

Sound advice!

A good quality brand such as M.T. isnt likely to sell you a poor perfoming fuel! But just to throw another spanner in the works hahahaha! What amount of nitro % does anyone prefer and why? More power is always good and so is better throttling, but what about reliability? are thier diffrences between 2 & 4 strokes as far as the best amount of nitro to use? I'm using a 5% mix at the moment, but have been thinking about a 10 or even15% mix.

 Any thoughts?


Jonathan Brooks23/06/2008 14:56:00
67 forum posts


I use 5% in everything but do have some 10% for my smaller engines
(enya 15) and for those very cold mornings - ie the ground is hard with frost. I also change the plug at this point - different heat range etc.

Laser engines have no nitro reqs and they must be one of the most reliable engines around.

I have had a few J'EN engines recently - and very happy i am with them too. They state that to go from the suggested 5% to 10% will raise the compression ratio enough to require you to shim the head and they duly supply shims though not advised. Seems bonkers to me, if you need more power firstly try a different prop then a more powerful engine or throttle pipe or something.

My experience is that if your engine is tuned properly and it is not over or under propped, throttling is so fast you would need to be a complete perfectionist to notice the difference.

General sport engines are so well engineered nowadays and there performance to capacity has come on so far that once again not worth going outside manufacturers recommendations.

I am not a patternship expert and these guys seem to use a lot of nitro - and there reasons will be 100% valid. Their reqs are different to the average sport flier - anyone willing to expand on that.

 Also, check out the price difference - i'll stick to lower % nitro.

Malcolm Fisher23/06/2008 17:52:00
641 forum posts
7 photos

Cost has always been a factor in my fuel choice and why I almost always ran on straight fuel until I got brand new engines where the manufacturer said to use 5% nitro.

 When I first started using engines, I chose diesel because, at the time, fuel was the same price - half a crown for half a pint. Diesels didn't need batteries, had no plugs to "blow" and were more economical as well. Now it's a different story - diesel fuel is much more expensive than glow. Had I access to cheap ether as I used to have when I worked in a lab years ago and could get it as a "staff purchase", and mix my own brew, diesels would be my preferred IC power source

I don't know if the ruling still exists, but for competition purposes only straight fuel was allowed by SMAE/BMFA, and I reckoned that what was good enough for the competition guys was good enough for me...

Owen Hailey14/07/2008 21:36:00
391 forum posts

Hi all.

Castor is the best oil for sticking to metal there is, and as a ex motor cycle racer we aways used caster and if you took an engin to bits it was as clean as a new pin in side, wheres sinthetic oils get very black and what is this black it is your metal wearing away so if you ask the old school engine builders thay all say castor. I also know that the move away from castor to sinthetic is mainly for it makes less mess of you plain.

all ways oily Owen.

shades15/07/2008 14:48:00
66 forum posts

Hi Malcolm,

I have just quickly read tthrough the above. Getting back to your original question, you must bear in mind that the rotary engine runs work in an entirely different way. My mate has a wankle rotary in his RX7 road car and has a huge knowledge of this engine. The compression is achieved by a seal on the rotor tip, this needs to be well lubricated at all times. Even though it is a high spec engine, (though simple in it's operation), he still uses basic mineral oil in the sump, because the engine is designed to burn some of it to lubricate the seals. Using synthetic oils can apparently gum up the seals.

 So, I would guess that the same applies to your model engine. So it seems entirely logical to me that you should indeed use castor oil in your fuel mix.


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