An Update on Ethanol Fuel Use

I keep running into claims that ethanol destroys engines or fuel systems,  primarily from the small engine,  boat motor,  and airplane people.  Airplanes are a separate subject,  since the federal aircraft regulations resist the change to less-susceptible materials,  even those known to be needed with the newer low-lead aviation gasolines (100LL).  As for the rest,  there are 4-stroke and 2-stroke types,  and there are automotive and lawn equipment types. See also "Aviation Alternative Fuel Compatibility Issues" dated 11-3-13.  

See Update 9-26-16 at end of article

2-Stroke Equipment

I cannot speak to the effects of stiff ethanol blends in 2-stroke engines,  other than routine use of what is now sold as “unleaded regular”.  That fuel is a nominal maximum-E-10 material,  that usually tests near E-8 when I check it.  I use it in my weed-eaters and my chain saw,  which are all 2-stroke. 

I have not ever added any extra ethanol to my 2-stroke fuels,  since these also carry the engine lubricating oil in solution.  I often clean greasy parts with ethanol,  so I naturally worry about stiff blend effects on critical engine lubrication.  10% ethanol seems to me to be no problem,  however. 

I have two weed-eaters,  one (a Ryobi) very old,  the other (a Sears Craftsman) only about a year old as of this writing.  My chainsaw (also Sears Craftsman) is about 4-5 years old.  All of these run on “unleaded regular” with 32:1 oil.  “Unleaded regular” has been a nominal E-10 material throughout the life of all but the oldest (Ryobi) weed-eater. 

There have been lots of complaints about dirt clogging things,  and fuel components “dissolving”,  and the “need for engine overhauls”,  ever since the advent of E-10 as “unleaded regular”.  Honestly,  I have seen none of these troubles,  but then I keep my machines clean,  and stored out of the weather. 

I believe that most of these “troubles” can be traced to the solvent action of the ethanol acting upon pre-existing serious dirt and water contamination,  which really should not have been there in the first place.  I also believe there has been a lot of predatory “repair” activity because of these effects:  expensive engine overhauls that did not need to be done.

If there are pre-existing “water bottoms” in the fuel tank,  then the ethanol in a blend fuel will pull it into solution,  right up to the fairly-unpredictable phase-separation point.  An engine set-up for gasoline (even an E-10),  will not run on the wet ethanol in the bottom layer of a phase-separated tank.  You do not need an overhaul,  all you need is to drain the tank and fuel lines,  and replace with fresh fuel.

If there is pre-existing “dirt” in the fuel tank and lines (usually gum and varnish deposits),  the solvent action of the ethanol in a stiff blend will “mobilize” this debris all at once,  which lets it travel downstream into fuel pumps,  fuel filters,  and carburetors. 

It usually won’t hurt the pump too bad (although check valves can leak because of grit blocking full valve closure).  But,  filters can clog up completely,  and the small passages and metering jets in carburetors can get plugged up.  You do not need an engine overhaul for such problems.  You need a clean fuel tank and flushed lines,  a carburetor kit,  and maybe a rebuild kit for any fuel pump that you might have.  (Most equipment is gravity-fed without a pump,  however.)

The only trouble I ever experienced was with the older Ryobi weed-eater,  and I cannot trace it conclusively to ethanol in the E-10 that passes for “unleaded regular”.  This machine is several years old,  with a very poor sealing design for the fuel lines coming out of the fuel tank.  I think age and heat have caused the polyethylene tank to shrink,  and the too-cheap plastic fuel tubing to harden.  I honestly think this would have happened even if there had been no ethanol in the fuel,  precisely because I have seen it before there ever was an E-10,  meaning I have seen it for many decades. 

4-Stroke Lawn and Garden Equipment

The very same “housekeeping” considerations apply here as for 2-stroke equipment just above.  You do not want any dirt or water bottoms anywhere in your fuel system.  However,  you can run up to 35% ethanol in your fuel,  and pretty much expect the same power and fuel consumption as on straight gasoline. 

The stiffer blends will be even more prone to pick up dirt and water bottoms,  causing the same troubles discussed above.  You simply avoid those problems,  it is easy to do.  Keep your equipment stored out of the weather,  and periodically clean the contamination out of your tanks and carburetor float bowls.  You can do this job yourself,  and you don’t even need a new float bowl gasket every time,  contrary to what “they” tell you. 

Here is my experience with a John Deere SX-75 riding lawnmower dating to 1987,  a Troy-Bilt wood chipper about 4-5 years old now,  a Sears Craftsman small push-type power mower dating to sometime in the late 1970’s,  and a Yard Machines riding mower of recent vintage,  that I acquired “used” about a year ago.  All of these run on nominal E-35 blend,  ranging from about E-28 to about E-38 in actual blend strength.  This is a lot stiffer than the nominal E-10 that is “unleaded regular” today. 

The John Deere has run on E-35 since the spring of 2008.  It has a polyethylene fuel tank,  neoprene fuel lines,  a polypropylene fuel cutoff valve,  and neoprene seals and polypropylene parts in its aluminum carburetor.  That’s 5 years’ exposure to date,  without one single failure of any fuel system part.  I have never overhauled its engine,  and judging by the way it runs,  I won’t need to for a long time yet.  I do blend 20% Lucas Oil Stabilizer into its engine oil. 

The Troy-Bilt wood chipper has run on E-35 blends since I bought it 4-5 years ago.  It has similar fuel system materials to the John Deere.  I have experienced no troubles at all with it. 

My very-old Craftsman push mower has run since about spring of 2008 on E-35 blends.  It has the same selection of fuel system materials as the John Deere.  I have had no troubles with fuel system parts other than a primer bulb on the carburetor that failed this year,  after having been installed 2-3 years ago. 

It failed by cracking,  but the cracks were on the outside surface propagating inward,  not the inside surface exposed to the fuel.  I have to conclude that this replacement part failed prematurely from inferior material selection,  with UV light and ozone in the atmosphere being the real cause of part failure.  The previous part was “real” neoprene,  and had lasted for some 3 decades in the same circumstances. 

The Yard Machines riding mower has run for about a year on E-35 blend fuel without a parts failure.  It does not have a simple carburetor.  Idle is controlled by devices that I do not yet understand,  and seems to behave as if the mixture is too lean on cold start,  when using blends.  I compensate by using the choke until the machine is fully warmed to full working temperature.  That takes care of it,  quite well enough. 

Automotive-Type Equipment (5 Vehicles)

I have so far exposed 5 vehicles to high-concentration ethanol in their fuels,  3 of them blends in unmodified vehicles,  and 2 of them straight E-85 in modified vehicles.  The unmodified blend fuel vehicles are a 1995 Ford F-150 XLT (the “ethanol Ford”),  a 1998 Nissan Sentra GXE (the “ethanol Nissan”),  and a 1960 VW beetle.  The modified straight E-85 vehicles are a 1973 VW Beetle (the “ethanol VW”),  and a 1944 Farmall-H tractor (the “ethanol Farmall”). 

The age of all of these vehicles belies the EPA’s concern about exposing older vehicles to ethanol.  I have experienced no troubles in any of them that are traceable to ethanol exposure. 

                Ethanol VW on Straight E-85

The 1973 ethanol VW had a high-time (worn-out) engine and transmission when I started this experiment.  What I found was that there are 3 things required for a successful conversion in a modern over-square,  high-speed engine:   (1) modified mixture ratio at idle,  off-idle,  and full speed,  (2) a significant advance in ignition timing,  and (3) extra intake manifold heating to compensate for a harder-to-vaporize fuel.  This particular engine was 1585 cc displacement. 

My first conversion to E-85 fuel was accomplished 10-29-2006 at odometer mile 231,626.  I went through several iterations and a couple of carburetors before I hit upon the items that worked for modified carburetion and timing,  plus the use of 20% Lucas Oil Stabilizer,  by about 12-17-2006 at odometer 232,269.  In that winter weather and the following seasons,  I found and finalized my added intake heat rig by about 8-12-2007 at odometer 235,105. 

It wasn’t until all 3 items were finalized that relative performance indices (ethanol vs gasoline) were finally established.  The energy conversion efficiency was verified by two independent measures to be nearly factor 1.2 larger on E-85 relative to the E-10 that is unleaded regular.  This partially offsets the drop in volumetric heating value,  so that fuel mileage on E-85 is about 80-85% that on gasoline,  not the 70% one would expect from straight heating value ratios. 

I drove that car on straight E-85 until it was no longer needed,  and then I returned it to mothballs in its ethanol configuration on 6-9-2011 at odometer 250,321.  That’s an operational exposure to very high-concentration ethanol for about 4.5 years,  and about 19,000 miles.  If there was a problem with ethanol damaging anything in the fuel system or engine,  I would have found it in an interval that long!  There were no problems at all. 

This vehicle has a steel fuel tank-without-any-terneplate lining,  steel and neoprene fuel lines,  a polypropylene cutoff valve that I added long ago,  and an aluminum carburetor and aluminum fuel pump,  both with neoprene seals and polypropylene parts (including the bowl float).  There was also a nylon float-retainer part inside the float bowl.  I do not know all of the materials in the fuel tank quantity indicator device,  but it still seems to function without troubles.  The indicator readout on the dashboard seems to be worn out,  because I can influence its reading by hitting it with my knuckles.   Otherwise,  none of this ever showed any hint of any kind of failure. 

                Ethanol Farmall on Straight E-85

This vintage-1944 machine has a steel fuel tank that was severely rusted inside when I bought it used about 25 years ago,  a cast iron carburetor with a tin float,  and neoprene O-rings around the brass adjusting screws.  The fuel system has steel and neoprene lines,  plus a polypropylene cutoff valve that I added long ago.  The fuel strainer is glass and aluminum,  with neoprene seals. 

This old engine is a low-speed,  under-square design very insensitive to ignition timing.  So,  the E-85 conversion only required (1) mixture adjustment,  and (2) extra intake heat.  In this case,  I only had to drill out the seat for the already-adjustable main jet.  There was plenty of idle adjustment available to handle ethanol.  The extra intake heat took the form of a simple sheet-metal air-guide baffle around the carburetor/intake manifold,  to trap extra heated air coming off the radiator. 

I did this conversion 10-17-2006.  It has run on nothing but E-85 ever since then (to 11-2-2013 as of this writing).  That’s an exposure time of 7 years.  In all that time I have never had one single fuel system or engine part failure.  The tractor runs with less smoke and better power than it ever did in all the prior years running on gasoline. 

Here’s the really striking result:  since I began running this machine on E-85,  the pre-existing corrosion inside that ancient steel tank has nearly disappeared!  The supposedly-corrosive ethanol has evidently actually mitigated the pre-existing corrosion inside that tank!

                Ethanol Ford on Various Stiff Blends

This is a 1995 vintage Ford F-150 XLT pickup truck,  with the 302 (5 L) V-8 engine and electronic fuel injection.  The fuel injection takes the form of a fuel rail maintained by a fixed regulator at constant pressure difference above absolute intake manifold pressure.  Mixture control is by injector duty-cycle “open”,  controlled closed-loop to a feedback signal from an exhaust oxygen sensor,  with an open-loop stored-map cold start feature.  I have used 20% Lucas Oil Stabilizer in the engine oil for this vehicle since long before ever trying ethanol blend fuels. 

It was a fairly high-time engine when I started using blend fuels in the rear tank only 12-16-2007 at odometer 177,332.  I investigated blends from near E-10 to about E-50 like this.  Starting 4-3-2008 at odometer 181,140,  I used blends in both tanks.  I had pretty much settled on nominal E-35 blends in both tanks by 8-4-2008 at 184,215.  I still use these nominal E-35 blends routinely as of this writing (11-2-2013 at about 201,800 odometer). 

To date,  that’s about 6 years’ exposure to stiff ethanol blends (some 25,000 miles) on otherwise factory-stock materials.  In all of that time,  I have never had a fuel system or engine part failure.  That would be steel tanks and lines,  neoprene lines and neoprene seals everywhere,  aluminum fuel injector body,  and polypropylene and neoprene parts in the fuel injection body and the fuel injectors.  I do not know what the fuel tank quantity indicating devices are made of,  but they have never even changed their calibration in all these years of exposure to ethanol. 

                Ethanol Nissan on E-30-ish Blends

This 1998 vintage vehicle has a fuel-injected in-line 4-cylinder 1.6 liter engine.  It was very high-time when I started using stiff blend (nominal E-30) fuels in it,  essentially unmodified (although I did add a fuel rail tap for testing blend strength).  I was already using large amounts of Lucas Oil Stabilizer in this vehicle long before the blend experiments,  because of a serious oil leak in a front crankshaft seal. 

I drove it far enough,  in a condition like that,  for the old engine to wear completely-out at an odometer reading far beyond any reasonable expectation for life,  and then I overhauled that engine.  I still drive it on stiff blend fuels today.  I did not replace the catalytic converter at overhaul,  which is now far beyond any reasonable expectation for useful service life.  Yet it still functions!  Total exposure time is about 4 years,  and about 48,000 odometer miles. 

I began using blend fuel 8-2-2009 at odometer 186, 514.  This was an estimated E-43 blend for the initial tank.  After a bit,  I pretty much standardized on an E-30 blend,  although I once accidentally took it to an E-50 blend and saw the same kind of fuel mileage degradation that I saw in the ethanol Ford at that same kind of blend strength. 

I have used blends near E-30 in this vehicle through overhaul to the present day,  which is now almost 234,000 miles odometer (about 20,000 since overhaul).  The fuel system materials and fuel injection control are pretty much identical to the ethanol Ford,  just a different manufacturer.  I have replaced the instrument cluster (due to old age wear-out of the dashboard indicators),  but the tank calibrations have remained unchanged with the passage of time,  for each of the two different instrument clusters.  That tells me that the in-tank fuel quantity measuring equipment is unaffected by exposure to stiff fuel blends. 

I have not seen any problems induced by the use of stiff ethanol fuel blends.  In point of fact,  at overhaul,  the inside of the engine was comparatively very clean.  And as for the effects of using Lucas Oil Stabilizer,  the rod and main bearings,  which were “worn to the red metal” at overhaul at 214,447 odometer miles,  were not the cause of the overhaul.  In point of fact,  it was wearout of the timing chain tensioner.  It had worn through the phenolic,  so that the chain was “cutting” the steel backplate of the chain tensioner.  The Lucas additive really does arrest bearing insert wear!

Based on the timing of major accessory wear-out,  I estimated the intended design lifetime of the Nissan to be only about 150,000 miles.  Based on federal motor vehicle regulations,  the catalytic converter should last longer than the vehicle,  say,  about 200,000 miles.  Mine has seen significant ethanol fuel content since 186,000 miles,  which changes that expected outcome.  

Ethanol tends to strip carbon off of exhaust components (as demonstrated by tailpipe cleanliness in the ethanol Ford),  which would include the catalyst bed in the catalytic converter in the Nissan.  Accordingly,  my “evident catalytic converter life” of 214,000 miles-to-date is far beyond any ordinary reasonable expectation on gasoline.  Since the “mode of death” for cat converters is carbon soot buildup,  I have to conclude the ethanol content has extended my cat converter life by acting to strip out some of the soot buildup. 

This is in direct opposition to the “conventional wisdom” of the EPA:  that ethanol “might hurt” emissions control equipment,  something oil company lobbyists convinced them of.  In at least this one case,  ethanol content has acted to extend the operational life of emissions equipment. 

So,  “they” (EPA and the oil lobbyists) are wrong;  there is no reason to fear E-15 blends no matter the vintage of the vehicle,  and really no reason to fear blends up to about E-35,  based on my data.  There are some other researchers who have shown at least-E-20 to be OK.  So,  I am not alone,  although I may have gone farther than anyone else in terms of blend strength. 

                1960 VW on E-35 Blend

I pulled this vehicle out of about 15 or 16 continuous years in mothballs,  in the belief that I needed it.  I “woke it up” unmodified factory stock on E-35 blend quite successfully.  Then I found I did not need this vehicle on the road,  and returned it to mothballs.  There were no problems.  The materials were about the same as in the 1973 ethanol VW,  except that the older vehicle has no fuel quantity indicator at all. 

Mileage Trends Established with the Ethanol Ford (and Nissan) Data

Most of this is Ford data,  simply confirmed by experiences in the Nissan.  Mileage has been better than what one would expect based upon a simple volumetric heating value ratio.  Up to about 40-45% ethanol,  mileage seemed indistinguishable from that on plain gasoline.  Above that blend strength,  fuel mileage dropped very sharply.  And,  behavior was like late timing:  very smooth,  just fuel-consumptive.

It takes the averaging of multiple tanks over carefully-controlled driving cycles to establish these trends.  The “scatter” from tank-to-tank,  even with a controlled driving cycle,  is far larger than the trends reported here.  Judging it from one tank to the next is a very serious technical error,  contrary to the popular wisdom.  And,  not controlling the driving cycle very carefully,  greatly expands the natural scatter from tank-to-tank at otherwise “the same” conditions.  None of this is intuitively obvious. 

I have published mileage data plots for the Ford and the Nissan previously.  See reference 1 and reference 2.  Both show miles per gallon indistinguishable from plain gasoline up to around 40-42% ethanol in the fuel.  Above that blend strength,  mileage falls rather sharply.  Yet,  even at lower mileage,  the ethanol VW definitely showed experimental energy conversion efficiencies roughly factor 1.1 to factor 1.2 higher on ethanol,  than on gasoline.  Somehow,  these seemingly-conflicting results combine and unify into one picture. 

The simplest model is a ratio of volumetric heating values,  as a function of ethanol content.  That is not a realistic model,  as Figure 1 (below) clearly shows (the blue curve).    The second simplest model is a linear extrapolation between gasoline efficiency at factor 1 to ethanol efficiency at factor 1.1,  (red curve in Figure 1).  This one is better,  but still does not explain the observed constant mileage from 0% to 42% ethanol. 

The next simplest model is to suppose that the extra released heat from the higher-efficiency ethanol feeds back into the efficiency factor for burning the gasoline component.  If you assume this effect is linearly-proportional to ethanol content in the fuel (and it may not be),  then you get a curve shape as in the green curve of Figure 1.  When I assume a proportionality constant of 0.4 for that feedback effect,  I get the plotted curve,  which pretty-well matches the Ford and Nissan experiences. 

These effects are very fuel species-dependent:  for the very same alcohol efficiency and feedback factors,  the far lower heating value of methanol gives an entirely different curve shape with blend strength.  This is shown in Figure 2.  I didn’t do it,  but similar different curve shapes would obtain from fuels like isopropanol and butanol,  even something like ethyl tertiary butyl ether (ETBE).  One would have to determine the relative fuel energy conversion efficiency factors from neat fuel tests.  The feedback factor has to come from blend fuel tests (whichever value matches the observed shape). 

Since the feedback factor of 0.4 that I have,  came only from ethanol testing,  only Figure 1 is “reliable”,  and only to the extent that the feedback effect is linear with blend strength.  Figure 2 is nothing but an educated guess for the moderately-similar methanol.  I did not feel educated in the least,  regarding guesses for propanol,  butanol,  or ETBE,  so I did not create any plots for them at all. 

Concluding Remarks

What I have to offer here is really in respect to ethanol-gasoline blend fuels,  not “neat” fuels.  Ethanol is only mildly corrosive,  compared to high-aromatic gasoline’s very mildly corrosive effects.  Methanol is far more corrosive.  Propanol and butanol are considered to be relatively non-corrosive.  The experimentation with which I am familiar found ETBE to be rather non-corrosive. 

You have to balance corrosivity effects against heating value and mileage effects.  The heating value effects are relative to some sort of a realistic energy-recovery model,  not just the ratio of volumetric heating values (as is “customary”,  but is wrong).  It’s a judgment call,  no matter what. 

Corrosivity effects are inherently empirical.  I hope the accounts here add to that empirical database.  The “conventional wisdom” is simply wrong about ethanol and corrosivity,  as regards commercial and automotive applications. 

Aircraft applications I will cover separately. 

See also references 3 and 4.

Update 11-4-13:

Taking into account my automotive,  small engine,  and aircraft experiences,  I would assess things as follows:

The automotive industry has long adopted materials compatible with high aromatic and ethanol content in gasoline.  That plus flex-fuel cars has driven the supporting parts industry in that direction for decades.  As a result,  you can reliably use blends or convert to E-85,  pretty much in anything from modern to very old.  And I do mean many decades old!

It appears to me that the 4-stroke small engine folks have also largely made the transition to ethanol-compatible materials.  I’m not so sure about the 2-stroke small engine folks,  and I have not run any stiff blend experiments in 2-stroke because of my preconceptions regarding lubrication.  E-10 seems to be OK in 2-stroke,  though,  and based on that,  I don’t have much concern about E-15 (it’s just not that different). 

I don’t think the boat motor folks have made the transition to ethanol-compatible materials yet,  not even on the 4-stroke side of the house.  It’s boat motors and 2-stroke equipment that I hear the most horror stories about.  (I haven’t really investigated this,  so my perception is only just that: a perception.)  If there was going to be a problem with water bottoms,  I would expect to see it in boats,  though. 

The light aircraft industry is still using the same materials they were using half a century (or more) ago.  Many of these are not even good for high-aromatic gasoline,  not to mention ethanol.  Commercial aircraft are today nearly all turbine,  for which biodiesel content in the jet fuel is proving to be a good fit (that’s a another whole topic area not discussed here).

Bottom lines:

Automotive:  feel free to experiment with stiff blends and neat ethanol.  The materials in common use for the last few decades seem to support ethanol compatibility,  by and large.  No mods necessary up to about E-42,  although I don’t recommend over E-35 because of minor cold start problems.  Conversions to straight E-85 are easy,  but will be successful only if you do all 3 required items (mixture,  timing,  extra intake heat).

4-stroke small engine:  feel free to experiment with stiff blends up to E-35 without mods.  I’d not recommend neat ethanol or E-85 conversions,  because the carburetors do not have removable jets and are therefore so very hard to modify.  It’s very hard to change the timing in a magneto ignition,  too.  The supporting parts seem to me to be largely ethanol-compatible in recent years.

2-stroke small engine:  I personally would not experiment with stiff blends in these,  because of lubrication fears (oil-in-fuel,  with an oil solvent also in the fuel?),  and because the supporting parts do not yet seem to be very ethanol-compatible.  Wait till the supporting parts industry has made the transition. 

4-stroke boat:  you can try stiff blends in unmodified engines,  but be aware that supporting parts may well be incompatible with ethanol.  You will have to determine the neoprene/polypropylene issues for yourself.  I’d rather wait until the supporting parts industry has made the transition,  before I went above about E-15.  If your parts are compatible,  up to E-35 should work just fine. 

2-stroke boat:  same as 2-stroke small engine,  and for the same reasons. 

Gasoline airplane:  you need an otherwise-compelling reason to do ethanol blends and conversions,  and you will run into incompatible materials and metal corrosion problems everywhere you look.  But it can be done.  And it does work. 

Turbine aircraft:  out of scope here.  Biodiesel blends do work just fine,  though.  

Update 9-26-16:

              From Biofuels Digest 9-25-16:

              DOE Study

In Colorado, a study conducted by DOE’s National Renewable Energy Laboratory (NREL), found that the petroleum components of ethanol-blended gasoline become degraded and unfit for use in an engine long before the ethanol portion takes up enough water to cause phase separation in the fuel tank. “Phase separation” occurs when an excessive amount of water is introduced into the fuel tank leading the ethanol and water to mix and sink to the bottom of the tank. In other words, gasoline becomes “stale” and unusable before water uptake by the ethanol component becomes a concern.

As part of the study, NREL scientists stored gasoline-ethanol blends ranging from E0 (0% ethanol) to E85 (83% ethanol) in actual lawn mower fuel tanks over several months in a climate-controlled chamber meant to replicate hot, humid environments like Houston and Orlando. The samples were tested at regular intervals for evidence of gasoline weathering and water uptake. In every case, the hydrocarbon components of the fuel became unfit for use in an engine before water uptake became a concern.

For gasoline-ethanol blends, it often took more than three months for phase separation to occur, meaning the fuel had already weathered to a point it was unusable. “In a small engine fuel tank in a constantly high-temperature, high-humidity environment, it takes three months or longer for E10 and other ethanol blends to take up enough water for phase separation,” the study found. “This confirms the statement by Mercury Marine that water uptake in E10 blends ‘…does not happen at a level or rate that is relevant.’”

President and CEO Bob Dinneen offered the following comments on the new study:

“Simply put, critics who continue to suggest E10 is a problem for small engines and boat motors are all wet. This research from NREL clearly demonstrates that gasoline goes bad long before the ethanol in the tank could cause any problems due to moisture uptake.

“Every manufacturer of small and off-road engines has approved the use of E10 in their equipment for many years. If owners of this equipment simply follow the manufacturers’ recommendations for fuel, maintenance, and winterization, they won’t have any issues at all. But, as this study shows, letting gasoline sit in your tank for extended periods of time is likely to cause some issues—irrespective of whether the gasoline contains ethanol or not.”

My take:  the water problems that small engine and boat motor owners report are due to the item being left out in the rain,  not the humidity.  The fuel tank caps have air vents.  The rain gets in that way.  Plus,  many folks are using fuel more than 3 months old.  Both a recipes for bad performance and maintenance problems,  even with zero ethanol in the fuel.  

References

1.      1. Gary W. Johnson,  “Stiff Blend Effects in Gasoline Cars”,  posted 11-122-2010 on http://exrocketman.blogspot.com

2.      2. Gary W. Johnson,  “Nissan Mileage Results on Blends”,  posted 11-17-2010 on http://exrocketman.blogspot.com

3.       3. Gary W. Johnson,  “Biofuels in General and Ethanol in Particular”,  posted 8-9-2012 on http://exrocketman.blogspot.com

4.     4. Gary W. Johnson,  “Ethanol and Emissions Control Functionality”,  posted 11-15-2012 on http://exrocketman.blogspot.com

Figure 1 – Ethanol Model

Figure 2 – Methanol Model

Figure 3 – Modeling Equations and Data