Had a lot of water in my fuel

[nels]

Good explanations, thanks. So, if you have two ounces of water present and puddled in the tank, you would need about two ounces of alcohol to dissolve that amount of water in the remaining fuel that is present in the tank? Of course the fuel would need to be sloshed around a fair amount get the two mixed?

[mooniac15u]

6 minutes ago, nels said:

Good explanations, thanks. So, if you have two ounces of water present and puddled in the tank, you would need about two ounces of alcohol to dissolve that amount of water in the remaining fuel that is present in the tank? Of course the fuel would need to be sloshed around a fair amount get the two mixed?

You need molecular equivalents as opposed to mass or volume equivalents.  Water has a molecular weight of 18, ethanol is 46, and isopropanol is 60.  So to have a 1:1 molecular ratio you need a little more than twice as much ethanol by mass and 3 times as much isopropanol.  However, as @carusoam points out the optimal ratio is likely greater than 1:1 for solubilizing the water.  There's probably a maximum amount of alcohol you want to mix into the fuel before you start causing other problems.  Your best bet would be to follow POH guidelines regarding what type of alcohol and how much to use for a single tank full and then repeat a for a few fillups.

Agitating the mixture definitely gives best results but fortunately you have diffusion working for you even if you just let it sit.  Flying the plane probably provides a good bit of agitation.

[nels]

Great information! Nice to know about how much to use.

[nels]

Not exactly on the subject but sort of..... Does alcohol also pull water out of the atmosphere such as brake fluid which contains alcohol? Wheel cylinders and other brake parts tend to pit inside after years of service and I assume that it is from water absorption? Also, the inside of older steel fuel tanks seem to corrode badly above the fuel level due to the alcohol in present day auto fuels.

[carusoam]

This is where you find packaging becomes really interesting...

moisture and oxygen can penetrate ordinary plastic bottles.  Slowly over time...

To prevent this, multi-layer plastic bottles with special effort in their mechanical seal designs or really high tech seal material gets used... when being capped, it is done automatically to a torque spec.

ever notice adsorbents still getting used in medicine bottles?  They often are there to absorb moisture and O₂ .  

Beer is sensitive to oxygen flowing in, CO2 flowing out and water escaping...  special plastic bottles are used for this application, with very short use by dates... glass bottles and their metal caps use a polymer seal on the cap.

Read the packaging label.  It will have a few bits of interesting details... Use instructions, storage instructions, use by dating...

if the alcohol is put in the fuel to absorb moisture, it won't care where the moisture comes from.  Your tanks are open to the atmosphere through their vent lines.  Moisture is ever present...

realistically, how long this stays in your tank will be important.

Always follow the instructions to get the performance that is expected.  Then balance the logic with, 'is this snake oil provided by a less than respected seller.'  (PTK is always fighting this battle for oil additives)

There is always going to be equilibrium at work.  It can only adsorb so much before it becomes inactive at absorbing more...

in case I forgot, follow the instructions.  Consult a mechanic...

Stand by for a real chemist's opinion...

Best regards,

-a-

[mooniac15u]

On 11/6/2016 at 8:08 AM, nels said:

Not exactly on the subject but sort of..... Does alcohol also pull water out of the atmosphere such as brake fluid which contains alcohol? Wheel cylinders and other brake parts tend to pit inside after years of service and I assume that it is from water absorption? Also, the inside of older steel fuel tanks seem to corrode badly above the fuel level due to the alcohol in present day auto fuels.

Both ethanol and isopropanol are hygroscopic so they will absorb moisture up to a point.  As @carusoam points out, the alcohol doesn't care where that water comes from.  Fuel tanks have vents so they are open to the atmosphere but the amount of water transferred to the interior of the tank is likely limited due to the relatively small openings.

Ethanol does tend to promote corrosion of metals but I don't think there is ethanol in DOT 3 brake fluid.  I think the alcohols in brake fluid are glycols which may have different properties.  I'm not sure what impact they have on metals.

 

[mooniac15u]

Here's the Mooney Service Instruction regarding use of isopropanol as a fuel additive.  Just keep in mind that most of the isopropanol sold as "rubbing alcohol" contains as much as 30% water.  Make sure you know what you have before you add it to your tank.

http://mooney.com/en/si/M20-64.pdf

 

[neilpilot]

The real value of using isopropanol is related to the variation in water solubility in 100LL.  In a typical scenario, you fuel in a relatively warm location and fly into a much reduced temperature (i.e. at altitude and/or to the frozen north).  As your warm fuel cools, water present in the fuel will come out of solution.  If it's well below freezing, ice crystals can form in your fuel in sufficient quantity to blind your fuel screen.  The real value of adding isopropanol is not so much to scavenge free water in your tanks (you should drain essentially all of that water out pre-flight), but to remove the additional free water as your 100LL cools, to prevent ice crystal formation.

I'm no chemist; I'm a ChE who has managed isopropanol by-product production and storage.  Currently have only about 300,000 lb left, since this plant is shutting down.  I use the red bottle (Iso-HEET), essentially pure IPA.  Do NOT use the yellow bottle, which is a blend of methanol and water!

 

PS -  

[carusoam]

Go ChE!  

Best regards,

-a-

[mooniac15u]

50 minutes ago, neilpilot said:

The real value of using isopropanol is related to the variation in water solubility in 100LL.  In a typical scenario, you fuel in a relatively warm location and fly into a much reduced temperature (i.e. at altitude and/or to the frozen north).  As your warm fuel cools, water present in the fuel will come out of solution.  If it's well below freezing, ice crystals can form in your fuel in sufficient quantity to blind your fuel screen.  The real value of adding isopropanol is not so much to scavenge free water in your tanks (you should drain essentially all of that water out pre-flight), but to remove the additional free water as your 100LL cools, to prevent ice crystal formation.

I'm no chemist; I'm a ChE who has managed isopropanol by-product production and storage.  Currently have only about 300,000 lb left, since this plant is shutting down.  I use the red bottle (Iso-HEET), essentially pure IPA.  Do NOT use the yellow bottle, which is a blend of methanol and water!

 

PS -  

Draining excess water via the sumps was discussed. The open question was whether very small amounts of residual water could be eliminated by adding alcohol.  Isopropanol helps with both phase separation and freezing point depression regardless of the source of water.

Pure gasoline can only hold about 0.03% water by volume at normal ambient temperatures where a 10% ethanol blend can hold about 0.5%. Either way a small amount of isopropanol won't add a lot of capacity but it will help.

[Yetti]

Alkeehol will attack all your rubber in the rest of the fuel system such as o rings in the carburetor.  What makes the current mo gas crap is the alkeehol soaks up water it has a shelf life of about 2 months in Houston.   I am tired of rebuilding carbs on small engines

[jetdriven]

I switched to 100LL for all my lawn mowers etc and those problems are over.

[LANCECASPER]

I think I'd rather put pure gasoline in my lawnmower if available in the area rather than more exposure to low lead. http://www.pure-gas.org/