RC Fuels Nitromethane, Castor Oil, Synthetic, heli fuel, 4 stroke, etc...Fuel Q&A is here!

2 stroke fuel in a 4 stroke engine

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Old 10-01-2011, 12:21 PM
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jetblast96
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Default 2 stroke fuel in a 4 stroke engine

Hi,
Quick and very common question: Can you use 2 stroke fuel in 4 stroke engines?
For now the only nitro plane that I have has an OS FL70 in it which loves the S&W 15% 4 stroke fuel with a castor/synthetic blend (unknown oil content). I am soon going to get a new airplane, but there is no way that I'm going to buy a 4 stroke that costs more than the airplane this time around, so I'm going with a 2 stroke (likely an OS 46AX). Once this happens, I really want to try to stick with only 1 fuel for both of my nitro planes, and I have no clue how to do that.
Do you think that 15% nitro with 20% castor/synthetic would do well in 2 strokes and 4 strokes?

Thanks
Mike
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Old 10-01-2011, 12:29 PM
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Default RE: 2 stroke fuel in a 4 stroke engine

Yes.

Most current OS engines recommend minimum 18 percent oil; castor, synthetic, or blend.

In many cases, modern two stroke and four stroke fuels are identical except for the label. There are still some 'four stroke' fuels with low oil content but it is not as common as it used to be.

Contact S&W http://www.splube.com/contactinfo.html and they'll tell you what's in your current fuel. There's a good chance it is fine for an AX.
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Old 10-01-2011, 12:38 PM
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Default RE: 2 stroke fuel in a 4 stroke engine

Buy another 4-stroke. It will outlive many planes.
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Old 10-01-2011, 01:50 PM
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Default RE: 2 stroke fuel in a 4 stroke engine

2-stroke fuels with high castor work fine in 2-stroke engines, but NOT well in 4-stroke engines. I recommend 0-4% maximum castor in 4-stroke fuels for Saito and other 4-stroke engines. Too much castor seems to gum up 4-strokes pretty bad. A few purists prefer NO castor in their 4-stroke engines. I prefer about 2% castor to lubricate the bottom bearings and keep rust down a bit better than a 4-stroke fuel with no castor. You might look up an old article on Google, basic homemade model fuel as the search terms to give you an idea what and how much oil, nitro and methanol are in various fuels for engines in common use. I would not use 2-stroke fuels containing a lot of castor in any of my 4-stroke engines. My Saito formulation is 3.6% racing castor, 14.4% Klotz Techniplate oil (all by volumes) and the rest percentages clean, dry methanol. Works great in the .91 and even in the Saito radial 170. Hope this information is of help.
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Old 10-03-2011, 08:05 PM
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Default RE: 2 stroke fuel in a 4 stroke engine

I believe that S&W "standard blend" airplane fuel is 2% castor, 18% synthetic lube. This is perfectly suitable for a 4-stroke and for most 2-stroke engines. If your 2-stroke has plain bearings (bushed, not ball bearings) you might benefit from a higher castor content.

I was not aware that S&W produced a special fuel for 4-strokes. Call Stan (the owner) and ask. www.s-whobby.com
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Old 10-04-2011, 08:58 AM
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Default RE: 2 stroke fuel in a 4 stroke engine

It's in the center of the page. But, the way to find out what's in it is to call and ask.
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