Fuel Commentary

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Mixing Fuel

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Submitted by Terry Joe Sprinkle


Basic Homemade Fuels

Using reasonable care and good clean chemicals, you can make up a simple and effective model airplane fuel for your own use.  I personally use the formulations below for my engines, which include the OS .46 FX, OS .61 FX, K & B .61, OS .46 LA, Tower .40, new K & B .48 and TT pro .46.  These model airplane fuels cost me about $9.91 to about $10.31 per gallon for the last 10 gallons I made.  This includes purchase, tax if any, hazardous shipping ($12.00 UPS), regular UPS shipment charges, etc.   One problem that I have found is that all four of our local hobby shops sell primarily, if not exclusively, Cool Power green fuel.  This is only about 17% straight synthetic fuel, and it has no castor oil in it whatsoever.  This is, by Morgan Fuel’s own ads, inappropriate for ABC, ABN (and AAC) engines, but this is exactly the fuel over half of my own club members use.  Low lubrication fuels account for a lot of the cases of nickel liner separation in the OS FX series for example.   Not only that, but a number of pilots really run their engines lean and this compounds the problem, and leads to premature failure of an otherwise good, strong engine.   All of the following percentages are by simple volume.  You can use clean dry Pyrex measuring cups, the ones that hold up to 4 cups and also have a 1000 ml line at the top.  I personally make up 2 ½ or 5 gallons of fuel at once.  I would suggest that your find good, reliable, inexpensive sources of the following ingredients and share the list with members in your club who decide to mix their own fuel.  There is no reason for each club member to have to reinvent the wheel.  You should get a good high quality castor oil.  Bakers AA castor oil and Klotz Benol racing castor are among the very best.  Usually, you can get Bakers AA a little cheaper.  It is about $24.99 from SIG right now, and that includes shipping.  You might find it cheaper, but be sure to buy a good grade of castor oil to begin with.  Second, you can get Klotz KL-200 Techniplate oil from Tower Hobbies, Klotz and a number of go-kart sites on the internet.  Remember that KL-200 is pure synthetic, and KL-100 is 20% castor oil and 80% KL-200.  Third, I currently buy all my nitromethane from FHS Supply, Inc. , located just outside Clover, South Carolina.  They have an internet site.  I paid $28.00 per gallon, got FOUR gallons, paid $12.00 hazardous shipping and about $6.50 UPS shipping.  Remember that if you order ONE or FOUR gallons, you still pay $12.00 hazardous shipping fee, so order FOUR gallons and split them up among club members to save a little money.  This is excellent nitromethane and is 99.9+% pure.   The last ingredient is methanol.  I buy mine from a local performance (speed, racing) shop and pay  $2.50 per gallon.  Club members can usually find clean, DRY methanol for between $2.00 and $3.00 per gallon.  Last, I buy really heavy duty HDPE (High Density PolyEthylene) empty gallon jugs from FHS Supply, Inc. for $1.10 each, including the lids.  These gallon jugs are great to put your freshly prepared fuel in and are several times the thickness of the commercial fuel jugs.  I order a full dozen at a time, because it costs about $6.50 for shipping the dozen empty jugs. 

Now for a couple of simple formulations for the engines above:

1.  10% Bakers AA castor oil, 10% Klotz KL-200, 10% nitromethane and 70% methanol.  

For example, using a 4 cup measuring Pyrex cup (buy at the local supermarket), take exactly four cups (one 4 cup container full) of Bakers AA castor oil and put it in a clean container that can hold 2 ½ gallons, add four cups of Klotz KL-200 oil, then 4 cups of nitromethane and then 28 cups (7 full 4 cup measuring cups) and mix thoroughly.  I use a good clean 10-liter ( about 2 1/2 gallon Nalgene jug with a spigot for this or a 20-liter Nalgene jug with a spigot for making up 5 gallons at a time.  Mix well, allow to sit and then remix.  After making it up, then immediately fill up your clean HDPE gallon jugs.  Tightly cap them, you do not want them to pick up excess moisture from the air.  Store all chemicals at about 50 - 75 degrees F, keep the pure nitromethane in the dark.  Do this carefully, the METHANOL is the more volatile and flammable reagent, NOT the nitromethane.  It is okay to put the methanol in first, followed by the oils and then the nitromethane.  Be sure you have enough of EACH chemical before you make up the amount you are going to make.  If you do this, your fuel will turn out the same every time and you can depend on the fuel to perform properly.

2.  For those pilots who prefer a castor oil based fuel, you can use the following:

20% Bakers AA castor oil, 10% nitromethane, 70% methanol.  This is among the simplest fuels you can make.  I prefer the mix of castor and synthetic oil in 1. above and have been using it since Klotz KL-200 was first sold in 1958.

Many medium sized engines (e.g. .19 - .65) come with instructions to use a minimum lubrication of 18%.  There is good reason for them to recommend this.  Some of the control line folks even use 22-23% total oil in their engines routinely, including their ABC, ABN, AAC and similar engines.  Engines run on these fuels typically last for years and years.  I find that around 20% oil is fine for R/C use. Remember that larger 2-strokes and 4-strokes generally use less oil than this.  This formulation is a bit greasy, so direct your exhaust either down, or down your landing gear and it will keep most of it off your plane.  Using formulation 1. above, you will find that your engine runs cooler, runs strong and will last a LONG time, just like it should.  I am not afraid to lean out my engine a bit and enjoy it.  You will also find that your engines will generally run well somewhere between 5 and 15% nitromethane.  I use 15% nitromethane on my performance planes, like the Extra, Cap 232, etc., with either the K & B .48 or the OS.61 FX, but all my other planes for sport run fine on 10% nitromethane. Making up your own fuel, you know exactly what went in it and how it performs.  By the way, the K & B .48 is one STRONG engine, and I have it running on the CG Tiger .60, MORE than sufficient power.  I broke in six of those engines on 1. above and all of them are getting stronger, idle better with use and have a good transition from idle to lean and back.  I hope this is clear and of interest to your club members.  I will be glad to answer any questions they may have about mixing up their own fuels.   I mix up my own fuels basically for four reasons; because it is relatively inexpensive and very simple to do, I have done so for over 44 years now, because I can mix up a better fuel than the Cool Power green available to me at my local four hobby shops and because I know exactly what is going in my engines and can tailor it as I need to for a given engine. 

Happy flying in 1999.  Terry Joe

Terry Joe Sprinkle

The old fuel mixing dinosaur


These are some of the suppliers for these items.  It is always good to find at least 2 sources for each item in case one place is low or has to backorder your stuff.

1. Bakers AA castor oil (from SIG, other suppliers, by quarts, gallons, be sure it is Bakers AA castor, the good stuff) I paid about $24.99 a gallon, but that included shipping from SIG.

2. Klotz KL-200 Techniplate synthetic oil (Tower Hobbies, Klotz, go-kart places on the internet, should be under $6.50 per quart plus shipping).  Be sure what you are getting, KL-100 has 20% castor oil in it already, just use the right final volumes.   I buy straight Klotz KL-200 myself.

3. Nitromethane - FHS Supply, Inc. on the internet at http://members.aol.com/FHSoil/

(I order FOUR gallons at a time, that way I only get ONE hazardous shipping fee, same for ONE or FOUR gallons, I sell the other two gallons to club members at my cost) On my last four gallons, I paid about $28 a gallon, $12-13 hazardous shipping fee and about $8 UPS shipping to my door.  Some folks pay about $50 a gallon, but if you get more, you will save money on your nitro.  Store it in a cool place, in the dark, will store properly for a couple of years.

4. Methanol - get locally from a performance (speed) shop for cars, motorcycles, or from a go-kart place, (they all carry methanol, at least most of them do, should be about $2 per gallon low price, $3 per gallon high price).

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Updated December 25, 2002