BAS

My Feedback: (28)

Fuel man how much oil do i need to add in Ozs to bring some 16% oil up to 20% oil > I have some Wildcat premium fuel which has 16% total oil 80/20 blend I am going to be breaking in a Magnum 80 fourstroke and need to add some caster as they instruct at least 50% caster content for breakin. I need to know how many ozs of caster i need to add to bring it up to total oil content of 20%. Whats your opinion on caster content for Magum four strokes.

Fuelman

My Feedback: (6)

BAS,
General rule of thumb which will get you into the ball park if only adding oil is to add 1.28 oz of oil for every percentage point increase you want to go up in a full gallon. Keep in mind that this is not an exact method, to increase the oil content and keep the remaining components in the same factory made ratios, you will need nitro as well.
Your fuel has right from the factory, 20.48 oz of oil in it (at 16% content), a fuel with 20% oil by volume will have 25.6 oz of oil in it from the factory, the difference is 5.12 oz which is ecactly 4% of 128 ounces. Remember that adding 5 oz of oil will bring your nitro content of the overall solution down just a little bit.

BAS

My Feedback: (28)

Thanks fuelman that is the info i needed to know , Thanks Bruce

mrfliboy

Fuelman, let me go along with all the others that have complimented you on a very thorough forum. I still am a bit perplexed about old glo fuel. I recently purchased a large quantity of glow fuel for a song and a dance. In the beginning, I was mixing it up half and half with some wildcat 15%, the cheap fuel was 10% and I've been running 15% for years. Now that my fresh supply of Wildcat is depleted, I'm using the 10% now and having sputtering and such problems. Who knows how old the fuel is. Along with this large buy 16 gals, I also received a gal of Nitro. My question is, buy adding fresh nitro will i pep up the gas so to say or would it be better to add some fresh methyl alcohol to pep it up. I'm thinking there's a moisture problem, even though the containers were stored in a crawl space, cool and dry. Would either idea help or would I be throwing good nitro and good money (purchase methyl alcohol) away. Thanks in advance.

Fuelman

My Feedback: (6)

mrfliboy,
You can try adding some nitro to your fuel, but I'm afraid that you'll be doing nothing but diluting the contaminates, if in fact that there are any. You can try it on a small amount of the old fuel and see if it works. Keep aware that anything you add (nitro or methanol) will reduce the oil content, so be carefull.
Let us know how you make out.

mrfliboy

I added 6 ozs. Nitro (Klotz) to a gal. There was some noticeable improvement. Was actually able to do a couple flights without a dead stick. Still seems to be some hesistation in throttle response and from idle to full throttle. Not sure what to try next, probably go back to mixing 50/50 with fresh fuel. Thanks for the input and keep up the great work. Jon

John C

In the forum files concerning Cox Texaco improvements, a fuel made up of 15% nitro, 10% propylene oxide, 5% castor, 1% lubrizol is suggested. Can you comment on the propylene oxide - what is does and where it can be obtained? Also, could you compare this mix with the 0 nitro, 3% acetone mix discussed earlier.

FWIW, I played around with Sig 10% & Powermaster 25% nitro, and TD, Baby Bee, and Texaco heads yesterday, one and two head gaskets, and really couldn't get what I would call a significant difference in power or run times, although the 25% seemed to be more consistent. These were with a 7X3.5 Cox prop spinning about 9400 RPM in all cases. Temp 85F, 60% humidity at sea level.

Fuelman

My Feedback: (6)

John C,
I hate to admit it but I have less experience with the Cox engines than I have with everything else. What has been a reliable mixture range for us in the Cox 1/2A's and smaller is 15% nitro, 20% oil (50/50 blend of castor-synthetic) up to 30% nitro- same oil component. That is not to say that is the best formulations. Since I treat the 1/2A market as a custom blend, nearly all our 1/2A customers provide us with their formulas.
As far as the mixture you mention, it sounds like its a bit low on the oil content to adequatly protect the connecting rod/ piston arrangement in the Cox engines. Again, I stress I am of lesser experience on these engines and would be apt to take the experienced based advise of one who uses them a great deal. Lubrizol is a great additive and I have it available, but is by no means a replacement for large quantities of oil. Propylene oxide I stay away from, just too dangerous for my liking to keep around. It does however increase power in a similar fashion as nitromethane. I know it is used a great deal with some 1/2A competition and some in boat racing, for me to comment on its effect in the 1/2A engines may not give you the information you want. As far as where you can obtain it, many racing fuel distributers can get it ordered for you, it is very expensive, I think it now costs more than nitro so you might as well use nitro to boost performance.

John C

Fuelman,

Thanks for the insight. Looks like the 25% blend is as good as any to stay with.

John C

spitfireboy

My Feedback: (1)

BIGSTIK is right I was in Texas for 11 yrs and now in Calif. and the colors have always been the same

spitfireboy

My Feedback: (1)

Imac I run a Mokie 2.1 and use 20% to break in then 18% all caster engine runs great and cool

hauckf

Fuelman: I'm not trying to be picky, but I think your reply in post #127 is a tad off. To increase the oil percentage of a full gallon of fuel, a good rule of thumb would be to add 1.6 ounces of oil for each percent of increase, not 1.28 oz as stated in the post. To be exact, to increase to 18%, add 1.56 oz for each percent increase you want, to increase to 20% add 1.6 oz for each percent increase, and to increase to 22%, add 1.64 oz for each percent increase.

Also, adding oil to a gallon of fuel will lower the nitro percententage in the fuel as you stated, but the percentage of methanol goes down proportionally, so the ratio of nitro to methanol, the stuff that burns to produce power, remains the same. That's why adding a few oz. of oil to a gallon of fuel doesn't affect performance to any measurable extent even though the percentage of nitro in the final volume goes down.

Fuelman

My Feedback: (6)

Hauckf;
Lots of numbers, several ways to look at them. You are correct, to be exactly accurate the increase in contents needs to be taken into consideration. Let me try to illustrate what you are refering to for the modelers that might be getting lost with numbers.
If I were to make two gallons of fuel, for example two gallons of 10% nitro, one gallon has 18% oil and 72% methanol the other has 20% oil, 70% methanol, the contents would be as follows:
#1 (nitro to methanol ratio of 1:7.2)
N: 12.8 oz
O: 23.04 oz (18%)
M: 92.16 oz (72%)

#2 (nitro to methanol ratio of 1:7)
N: 12.8 oz
O: 25.6 oz (20%)
M: 89.6 oz (70%)

Now, if I wanted to take the 18% oil jug of fuel and doctor it up so it has around 20% oil in it, I would add 1.28 oz per percentage point increase or 2.56 oz total to the mix., the resulting mixture would be a total of 130.56 oz broken down as follows:

#1+ (130.56 oz, with the added oil), (nitro to methanol ratio 1:7.2, same as it started out)
N: 12.8 oz (9.8%)
O: 25.6 oz (19.6%)
M: 92.16 oz (70.6%)

Now, to make the fuel run exactly like a gallon of 10/20 factory made, you would have to adjust the nitro up 0.2% , the oil 0.4% and that would drop the percentage ( by volume) of the methanol down by 0.6%, making the chemical mixture , by percentage exactly the same as the factory made 10/20 fuel.

OK, lots to soak in. For the purpose and intent of the modeler that has a need to adjust the oil percentage of oil up a few percent, the ballpark 1.28 oz per percentage puts you in the right ballpark. For greater adjustments than just a few percent, a little simple equation is required. For modelers that require exact final proportions (assuming you are measuring by volume), here's the formula that works in english or metric usits of volumetric measure. this formula will not work when calculating by weight measurement since each component has different specific gravities, and it only works with one component alterations.
z(x+y)= x(s) + y

x= starting volume of fuel.
y= volume of oil to be added
z= final percentage of oil
s= initial percentage of oil

To use our example above of 10/18 fuel to start adding to make it a true 20% oil by volume. (You'll still need to add nitro)

z(x+y) = x(s) + y
.20(128+y) = 128(.18) + y
25.6 + .20y = 23.04 + y
25.6 = 23.04 + .80y
2.56 = .80y
3.2 = y

Now, using the formula, here's what we get so you have comparison to the above, lets call it #1B:

#1B (131.2 total ounces of fuel) (nitro to methanol ratio is still 1:7.2)
N: 12.8 oz (9.75%)
O: 26.24 oz (20%)
M: 92.16 oz (70.24%)

You folks can make your own discussion from here, so I hope this is clarified for the purpose of exactness. As I stated previously, the earlier 1.28 per percentage point gets you in the ball park. Now for the average flyer that adjusts fuel oil, lets keep in perspective a couple things; are you able to measure by volume this level of accuracy for the small amounts required in adding to a gallon. and how many engines can tell the difference between 9.75% nitro and 9.8% nitro or between 19.6% oil and 20% oil?

Very observent point Haukf, thank you for your contributions to the forum.

hauckf

I read fuelman's reply. and when all that smoke cleared, the fact still remained that the "general rule of thumb" of adding 1.28 oz of oil for each percentage point increase you want is incorrect. A much more accurate amount to add for each percent of increase when the target is in the 18 to 22% range is 1.6 oz. To illustrate this, let's look at the origingal question that BAS asked in post #126, which was "how much oil do I need to add in ozs to bring some 16% oil up to 20% oil".

BAS is trying to increase the oil content of a gallon of fuel 4 percentage points. 4 times 1.28 oz, the "ballpark" figure recommended by fuelman, is 5.12 oz. Adding 5.12 oz of oil to that gallon, would bump the oil percentage up to 19.2%, not the 20% BAS was aiming for.


The standard formula for adding oil to a gallon of fuel, the one that fuelman included in post #127, gives the correct answer, which is that BAS needs to add 6.4 oz of oil to the gallon of 16% fuel to get it up to 20%. Not coincidentally, 6.4 is 4 times 1.6, 1.6 being the more accurate "rule of thumb" when adding oil. Imagine that! And yes, I do think that there is a difference between 19.2% and 20%, and I'm pretty sure that most of us can see the difference between 5.12 oz and 6.4 oz on our measuring cups.

Looking again at fuelman's post #138, in both examples #1 and #2, if fuelman had added 1.6 oz X 2 instead of 1.28 oz X 2, he would have ended up with 20% oil exactly, not 19.6%.

OK, now lets now look at it from another direction. The standard formula for adding oil is:

Ounces of oil to add to a gallon of fuel = (D%-S%)*128/(100-D%)

where D% is the desired final percent oil, and S% is the starting percent oil. Dividing both sides of the equation by (D%-S%), we get the formula for determining how much oil to add to a gallon of fuel for each percent increase. That formula is:

Oz of oil to add per percent increase = 128/(100-D%)

Plug in any percent between 18 and 22, and you will get a number very close to 1.6. In fact, I challenge anyone to to come up the a D% (other than zero) that will give an answer of 1.28. It can't be done!

Bottom line, if even when advice is called "ballpark" or "rule of thumb" it should be best advice possible. If 1.6 oz gets you not only into the "ballpark", but in for very close to the right seat, why would you want to recommend or use 1.28 oz, a figure that is about 20% low? If fuelman wants to add 1.28 oz per percent increase, so be it. The rest of us should use 1.6 oz.

As for the discussion of the nitro content, if BAS wanted to duplicate 10/20 factory made fuel made from a gallon of 18/20 fuel, which is a question he never asked, he would indeed have to add both oil and nitro. The exact amount he would have to add to the gallon of 18/20 fuel would be 3.29 oz oil, and .37 oz of nitro. If that information is in fuelman's dissertation on this topic, I missed it. Actually, all he had to do was plug the numbers into the Excel spreadsheet I gave him, and he could have given us those numbers!

PS For those of you who use the metric system, the formula for the amount of oil to add to a liter of fuel for each % of increase is: ml per percent increase = 1000/(100-D%). I think. Let me know if I'm wrong. (Ya, like I have to ask! )

marikan1

Fuelman,

I live in Turkey. I have mixed my fuel to date. But now, I got a 4 stroke TT 91 engine, it is my first 4 stroke. Its instruction says, i should not use pure castor oil. I have read all messages about fuels. You recomend klotz oil for synthetic. But here, i can not find it or the genuine rc synth oils. I am wondering if i could use any automotive oils for synth? for example, castrol 2 stroke motorcycle oil that it is called TTS. Or another brand of 2 stroke motorcycle oil (shell, bp), of course i will mix it with castor.

Thanks.

Mehmet.

Fuelman

My Feedback: (6)

Mehmet,
I recommend Klotz only because in our country and some others it can be easily found.
No automotice oil I am aware of will remain in solution with methanol. I am not sure if the oils you mention will mix with methanol. I have been told that Motul Micro will mix well for model fuels and AeroSynth? is another one from Europe.
I am sorry I do not have any better recommendation for you that that.

ZebraOne

My Feedback: (8)

Fuelman

I've cleaned "wet" gloplug fuel by adding 2 pkgs of knox gelatin to the jug. Gelatin IS hydroscopic and will not adsorb meth or ethonol.
Tx fer from jug when gelatin stops swelling. Add another pkg to new container..
I used to make some very fine grappa. Almost 170 baum.

Just call me Rudolph
VERRY red nose
Zebra

shiroi51

newbie here. great wealth of info here, great job Fuelman! I have a question, and I hope it's now too basic to be posted in the fuel faq.

Why shouldn't fuel be stored on bare concrete/cement floors?

Fuelman

My Feedback: (6)

Shirio51
Fuel stored on bare concrete / cement floors has never caused me or anybody I know a problem. If you have fuel in cans, corrosion of the metal can could occur.

Keep fuel tightly capped, in a cool dry place, out of direct sunlight and you should be fine.

BAS

My Feedback: (28)

Fuelman i cant seem to get a answer to a question i had on nitro content for OS 160 twin 4 stroke. I like running Wildcat heli blend with 30% nitro and 18 to20% sythetic oil. Will this do any harm to my 160 if i keep the needles rich. It runs great in my Saitos and YS motors.

Fuelman

My Feedback: (6)

BAS,
I sent you a PM on this, sorry for the delay in responding.

roroman

fuelman: what kind of acetone is used for 0% nitro.? is it the one available at the drugstore?
.I am using a magnum 108 abc 2 stroke. I want to try no nitro, is this a good idea?thanks

Dr Nitro

roroman,
I used to homeblend a lot of fuel and played around with 0% nitro in some engines. I did use some acetone for cooler weather flying, about 3% by volume and it did help. I used the type of acetone that was available from an auto-body supply shop simply because it was available. Differences in acetone do exist, however I do not know what they are, just that what I tried seemed to help with transition on cooler days.
Your engine should do just fine on 0% nitro once tuned to it and the correct glow plug is found- try a hot plug with low nitro.

tripp3d

I'VE GOT GAS...

Fuelman

My Feedback: (6)

TRIPP3D
What can we help you with?
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