Fuel Dinosaur

Wanted to make some observations and reflections about fuels and fuel ingredients.

1. It is not always just synthetic vs. castor oil. Each has its own unique properties and there are virtues and drawbacks to each. Also depends on the specific engine and application. Often, but not always, a mixture of the two can be used to use some of the better properties of each.

2. Nitromethane adds some oxygen, gives a good idle and adds power in most applications. That being said, over half the world either cannot get, cannot afford or cannot even possess nitromethane in their country. After the Oklahoma City federal building bombing, we are lucky to still be able to get and use it.

3. Green, all synthetic 17% oil is, in my experience, not very suitable for ABC, ABN and AAC engines. "Run rich" is a good and lofty goal, but not always realized in practice.

4. NOT all commercial fuels have sufficient oil and the properties of some of these oils are mediocre at best. Apparently, Power Master and SIG and a few others still know this. (no, I do not work for either)

5. FAI fuel works well in engines designed for it, or with engines in which the top of the piston to head distance are decreased and a good hot plug is added.

6. Nitro - there are relatively few large suppliers of nitro. So long as it is high purity use it. Some sources contain at least one or two carcinogens, there is some nitroethane and a little nitropropane and other stuff, but the overall quality of nitro from good sources is quite good.

7. Castor - There are good sources of AA castor, Benol and other racing castors that are suitable for model fuels. Don't use medicinal castor, please. Also remember that a lot of oils you may consider may not even mix with methanol.

I hope this is received well. Some folks think saying stuff about fuel is akin to talking bad about their dog or their mother. :-) Enjoy your flying and treat your engines nice. Terry Joe (The old fuel mixing dinosaur)

bigbadbowtie

I have a question for you.....

Why is there such a HUGE difference in oil content for air based RC's and ground RC's.

Fuel Dinosaur

Ray,

The claim is that newer lubricants permit lower oil percentages on ground type RC. However, the issue is more complicated than that. First, there are racing fuels with moderate to high nitro and designed for power, throttle response and the like. For example, some racing fuels for cars only use 8% of which most is castor, at least in some. If you are not racing, a higher oil content might be indicated for routine runs Second, some readers might believe that this is the case across the board, but fuels in the larger bore ST and other large plane engines use 10% oil, although I use a formulation of 12% oil and they run great, even in the hot part of summer. A few modelers out there, if they are honest, will tell you when they used 5% turbine oil as their sole lubricant. Not even a clear solution, but it provides a measure of protection for an engine. Due to the chemical structure of some materials in the turbine oil, it is not a good idea to run it routinely much of anywhere. Another point is that at Perry two years ago, a number of boat racers were burning up their engines. They saved some engines with a little racing castor, surprisingly little to keep the lower end intact. These suckers COST a lot of money. The idea that one fuel fits all is at best a compromise, if not an illusion. I use 16-18% oil, of which 2% is Benol in my FA-91A Saito engines and they run great on 15% nitro. Might be able to use 10%, but they run very well on this fuel at 15% nitro. If you run 2-strokes and 4-strokes, you might keep it to 2 fuels. I would NOT run more than about 2% castor in 4-strokes, but I have seen modelers put that pink stuff in their 4-strokes. :-) If you want to see some good aero fuel, just take a look at what Jett runs through a brand new $300-$450 engine the first time! That is the time things are most likely to go to heck in a handbasket, so they are NOT going to run crap through that engine. I think that a lot of modelers miss the point when they complain about all the goo all over their wing and tail after a flight. That is what is on the engine inside. When it is nice and clean, that is not always the best thing. Pattern fliers tend to use all synthetic and many 4-strokers do too. Problem is in this fuel arena, there is a lot of heat (sometimes literally) and very little light

bigbadbowtie

I appreciate the info. I am a ground based RCer and have raced on a club level off and on for 8 years. I pretty much refuse to run the 8% stuff you are refering to. I ran Morgans Omega for years. I cannot count the times I was told that "airplane" fuel is going to ruin my engines. I can't get it anymore so Im running a wildcat car fuel thats 14%.

It seems to me that a ground based RC engine goes through some of the most most horrible conditions. They are wide open atleast 3/4 of the time while being loaded and unloaded countless times per lap. It just does not make sense to me that low oil is a good thing.
I can understand the throttle response and maybe a tad bit more RPM but at the expense of premature wear and tear....
Maybe I'm wrong....

I do know that a 17% castor/synthetic mix fuel won me a track championship 3 years ago. Ill stick with it!!

nullibiquitous

Why is medicinal castor a bad idea?

XJet

When it comes to protecting your engine, it's not so much the quantity of your oil that matters as the quality of it and how well you tune (in my experience).

I firmly believe that most people tend to run unnecessarily high oil percentages for two reasons:

1. because the oil they're using is not very good
2. because that's the way it's always been.

Obviously fuel manufacturers want to use the cheapest components they can -- because this means maximum profit. At the same time, they don't want to be held liable if someone's engine dies due to lubrication failure -- so they stick with high percentages so as to avoid the obvious accusations that would come from running lower volumes.

These two factors work nicely together -- just use lots of a really cheap oil and everyone will be happy. The engines are adequately protected and the manufacturer is safe from claims that their fuel stuffed an engine.

However, if you use a *better* oil you can use it at a far lower percentage and get some real benefits without compromising protection.

That oil will cost a little more than the old inferior oils -- but since less is used per gallon of fuel, the overal cost is unchanged, while performance is actually increased.

So why don't the mainstream fuel manufacturers just switch to lower percentages of better oils?

Well as I said before -- they daren't risk it -- for fear that if someone stuffs their engine through bad tuning, wrong prop selection or other factors, the fuel maker will cop the blame and their reputation/sales will suffer as a result.

Just look at how many Europeans are getting great performance and very long-lives out of their engines, even though they run 8%-12% oil. How can they do that? Why aren't their engines blowing up left, right and center?

Because they're running a higher quality oil than the stuff normally found in US-blended fuels.

Now there's nothing wrong with running lower performance oils in higher volumes -- if you don't mind compromising the maximum performance of your engine or spending more money than you really need to, but I'd rather take advantage of modern lubricant technology, get better performance, ensure maximum engine protection and save money -- all at the same time.

Fuel Dinosaur

I see your point in the previous post, but one problem folks do not seem to know. Despite all the hype, the more effective lubricant oils are quite expensive and most modelers will not pay for those oils, and some are specialty oils with relatively low production. Second, only in the U.S. and a few other countries do we even have the luxury of nitromethane. True it does help idle, and top end performance, but overseas, many engines are sold that are perfectly happy to run on FAI fuel. When we run low oil content fuels, we are largely compromising immediate performance for longer term output and lifespan. Another point is you seldom see an engine damaged from too much oil, but you will see a lot of engines nearly fried from using poor oils or too little oil. When you run your engine and see it really smoke when you land, you KNOW it has really been pushed to the limit or a little beyond? If you run many engines from about .15 size to at least 1.2 size on SIG 20% oil, half castor and half synthetic, they will be gooey and last a LONG time. You may need to clean them every few years, whether they need it or not. I can tell you that empirical experience mixing fuels for rat race and combat teaches you really fast how NOT to get a hole in the top of your piston or have the crankshaft crystallize on you and fly out the front of the engine. Speed eventers even learned that even more quickly. Also, back during the old King Orange Internationals held in Miami FL off 27th Avenue, we tried Klotz oils and in many applications, the oil alone did NOT keep engines from burning up. We still had to use castor, which has been in use for well over 50 years now. Engines have greatly improved and we can now use about .40 size engines to match some older .60 sized engines. However, in our 2-strokes, the basic parts and need for oil remain the same. I have to call it as I see it and find it not a good idea to run 4-strokes on the pink stuff with that large excess of castor. Conversely, running nice ABC, ABN and AAC engines on 17% all synthetic oil is not always a good idea for most modelers. I know a lot of modelers do, but that is akin to saying I jumped off my roof 8 times and never broke my leg. That does not mean that I want to do that. Except for extreme competition flying, it is probably better to err on the side of a little more oil than too little. Modelers are not going to pay, as a group, for very expensive oils, and many, unfortunately, are avoiding castor. The article on the evils of castor and its quality did not help much either to clarify some of the issues. Castor AA and Benol (and a few others) have been around a long time and have served us well. The old fuel mixing dinosaur.

Fuel Dinosaur

Medicinal castor is highly processed, it has been treated, titrated, deodorized and all kinds of things for U.S.P designation. In the process, a lot of the lubricating properties are decreased. Suggest you use Bakers AA from SIG, Klotz Benol or other high grade racing castor.

Jezmo

Hi XJet,

Got a an idea. Anyone here interested in spending 400+ dollars on a Dubb Jett pylon engine and running it on 8% synthetic oil to test the theory that it will be OK? I don't have the funds to try this but would be very interested in knowing how it works out. The reason I chose the Jett is because it is a very high quality piece and actually makes enough power to hurt itself if not lubricated properly. Any takers?[8D]

Sport_Pilot

It's the same as AA castor but tested for ricin poisen and other impurities. I have used it with no problems way back when.

bob27s

My Feedback: (19)

Not me

I've experiemented a bit with lower oil content, and different oils. Usually the engine performed ok, but there was no dramatic performance increase. Just in tests Ive gone as low as 14% total oil content (synth/castor blend). So.... question comes up..... why bother lowering the oil if it does not make a difference ?

Single point to watch out for is not the cylinder - it is the crankpin and rod that will wear/fail first (most likely). Engines that have light torque requirements (like some car engines) can get away with lower oil, partly for this reason.

Yes, there may be some outstanding lubricants on the market..... but consider carefully before trying something new.

Bob

XJet

Well everyone in our club has given the low percentage/high-quality oil option a damned good try and despite lean-runs, under/over-propping and burning many gallons -- all of the engines involved are running "as new".

It actually costs us quite a bit *less* per gallon to make this fuel than it did when we were using Morgan's or Klotz oils and I would say that (given the amount *I* fly), I will have saved enough money this season to buy a brand new engine -- even though I won't need one because, despite all the warnings from doomsayers, my engines are still in as-new condition with no measurable wear! (and I'm an engineer who designs and builds jet engines so I know how to measure very small amounts of wear :-)

I realise that there's a *huge* resistance within the modelling community to this low-percentage/high-quality oil concept so I'm more than happy to enjoy it while most others continue filling the fuel/oil-seller's pockets and doing little more than unnecessarily covering their engines and models in slime :-)

I seem to recall it also took a long time for the motor-car to catch on at the turn of the century -- there were those who said "you can't beat a good horse, they've been around for decades" :-)

bigbadbowtie

xjet... what oil are you using??

XJet

I'm using Cooper Fuels Liquifire Plus C oil. It's a castor/synth blend but they also have a pure synth for those who desire such.

Me, I run a lot of ABC engines so I like the extra lean-run protection that a touch of castor offers.

bob27s

My Feedback: (19)

Nothing at all wrong with trying something new and innovative. And as long as it works, no reason it shouldnt be offered main stream in the market place.

Lord knows I have tried everything from Ethanol, Hydrogen peroxide, and all sorts of fuel and oil alternatives. I even tried store bought vegetable oil once, just for goofs.

But to address commercial model fuel cost though, here in the USA, 80% of the fuel cost is a commodity price - in other words, the cost of the material is driven by "the market" or set prices by commodity exchanges. Methanol and Nitromethane both fall into this catagory.

Nitro is only produced by a few manufacturers here in the USA. Only a couple of those provide material for racing/model engine use.

Methanol is produced more widely, but again, it's price is market driven.

Distributors who market highly purified and repackaged versions of these products for high performance engine use will obviously mark up the price from the baseline market a bit. Competition does not drive these prices, supply and demand (and to some extent investor speculation) does.

So as noted, this comprises about 80% of the volume and total cost of US available fuels. Finding market prices for these items is not hard to do with a web search.

The lubricant and additive packages account for the other 20% of cost. These are not inexpensive items.

So you figure something like this rough though fairly representative example
10% nitro standard fuel, 17% oil, good methanol - one gallon - appx USA street price $10 (just a number here)
Nitro appx $40 per gallon x .10 = $4.00
Methanol appx 3.50 per gallon x .73 = $2.55
Oil (varies - from $16 to $25, assume $20) $20 x .17 = 3.40
total $9.95 (close enough)

Cut the oil in half, add more Methanol per gallon - nitro content unchanged
Nitro $4.00
Methanol (now appx 82%) $2.85
Oil (keeping price constant) $20 x .085 =$1.70
Total $8.55 per gallon

Again, just an example. But the examples scale up and down proportinally
It does show there is a cost savings from cutting the oil/additives in half - appx cost reduction of 14%.
So yes, you could save about $1.50 per gallon, in this example.

Or, the price of the oil can be up to $36.47, to result in the same $9.95 street price, with the expectation of better engine performance.

A significant cost driver? Perhaps. But figuring I might be saving $1 per gallon (all things considered), and assuming I burn 2 gallons of fuel a month (extention to $24 - including winter) it is hard to argue the point I would be able to buy myself a new engine each year due to savings. But it might buy me a free month of fuel.

Performance driver? Maybe. Less oil means less to interfere with the fuel burn process. The better oil should improve performance by reducing friction. How much more performance ? Idunno. Ive seen anything from Zero to maybe 500-800 rpm dropping from 18% oil to 12%.

It all comes down to what you want, what you like, and what your requirements are for cost/performance.

Bob

Fuel Dinosaur

Bob,
Good reply for a somewhat complex subject! No too long back, you could get methanol for well under $.85 a gallon in bulk, but NOT now. Also, nitro remains expensive and there are not in practical terms, very many U.S. sales sources for bulk nitro. Did any guys you know try Mobil turbine oil in their engine at about 5%? [] Showing my age a bit, folks showed up at the King Orange Internationals in Miami with the then new Klotz oils, propylene oxide, shoe polish (nitrobenzene), acetone and heaven knows what else. That is when speed, rat race, C/L combat let you use your own brew. Seems like the first thing we learned how to do is burn a hole in the top of the piston, or more often, just destroy the lower end of our engines. If we were really "good", we could crystallize our crankshafts. Fuels were first arrived at, for the most part, empirically, that is, we stayed with what worked and would try anything (once) for competition. I always note with interest so many younger modelers who do not use any castor in many of their 2-strokes. Looks like allergic reactions to the smell of castor (or the old taste) have swayed folks entirely away, that and scare articles on the evils of castor and how much of it is bad. Some modelers are trying, perhaps by serendipity, to see just how little oil they can run in a model engine. My experience is that if it is your engine and you are willing to pay the penalty, you can drop the oil and maybe get a few hundred more rpm. In some events, that is important, but for sport flying, my sense is that it really is not. Just a few reflections from an old goat.