Hi.. what can I add into the Nitro fuel to increase the lubricant %? I can't seem to find any castor oil off the shelfs.. is there anything I can use from the motorcycle/car engine oils range?

(The shops here frequently run out of Heli 20/20 fuel, thus I am thinking of getting a Plane's 20/16 fuel and top the oil content up to 20%).

I know it might sound strange and alot of people will go "why did you do that". But I recently wanted to try something different (and I did it on a cheap experiment engine). I used normal 2-stroke petrol (gasoline) oil. The oil I used was "Shell 2-stroke Lawn Mower" oil. To be exact. But I guess you can use any regular 2-stroke oil mix for gasoline engines.

The engine ran fine, it spluttered abit (as in it was a bit rich) I just retuned her and she ran like a dream. She was smoking heaps because of the extra oil. But seeing alot of smoke from these engines, is a very healthy sign for them. Ive been using the oil ever since, ive only been adding little amounts. Probably around 50-75mls, to a 1litre bottle of fuel. Had no toruble with it.

Try it, if you dont like, then dont use it. But atleast try it once.

How can I tell how much to add to bring 1 gallon of 16% oil content to 20% or more?

If we are talking US gallons, a gallon is 128 liquid ounces. So 1% is 1.28 oz. So 5 ounces is about what you want to add. This is not exact, because you now have 133oz. Be sure and check any oil you want to use to see if it will mix with your fuel.

thanks.. i will try it out when I am out of my 20/20 supply.

The same thing happened to me when I tried to mix the oil with the fuel. I tipped in the oil slowly and you could clearly see all the blobs of oil in the fuel. It was like oil-meeting-water. You could see the blobs. So i shook up the bottle very fast and hard and got it fully mixed in. I have left my fuel for a few weeks now with the 2 stroke oil still mixed with it, and to my suprise it hasnt seperated!

I thought over time, it would seperate, but I couldnt see any such thing. But of course, before I used it again, I did shake it up abit more, just to mix things up again. Works like a treat.

I noticed that for some engines like OS, they state that it is not advisable to use a lower nitro %... I notice there are people who says either:

1) they have no problems, all they need to do is to lean the engine a little.
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2) they run into issues, because the engine runs a lot hotter than it used to.

Anyone knows the real reason behind that leads to the manufacturer stating this clause in the engine's manual?

Remove the head shim and running lower nitro should not present any problem. Re-tuning will be necessary any time anything is changed (low speed and high speed)

As far as adding petrol two stroke oil, don't do that. Just because you can get a petrol based two stroke oil to mix with methanol/ nitro fuel in small amounts does not mean it was designed for use in glow engines. It will increase the amount of hard carbon buildup inside your engine.
Stick with a castor or synthetic product intended for methanol or nitro. Blendzall, Klotz Techniplate, and some Maxim products will be more suitable. Ask around at a high performance motorcycle shop.

The other alternative is to use the standard airplane fuel and just insure you do not run it lean.

I did gave it a go.. added some 2T into the fuel... the 2T was too thick. Couldn't mix well.. and the engine ended up over heated.... dump all the 2/3 gallon of fuel away.

Oh well.. guess I will stick to using 20/20 fuel and fly less till the stocks are in.

Thank you everyone for your replies.