Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

    Leaving gas in OPE over the off season is often fingered as the culprit for varnish buildup.  I’ve come across people who have left gas in their tanks without a problem over many years.  It’s probably due to storage conditions like temperature, dampness, the amount of gas, venting in the carb and if there’s a gas stutoff. 

   If someone stores a piece of OPE with a full tank in a hot shed with no gas shutoff then what evaporates in the carb bowl would be replenished from the main tank over the off season.  If there’s a shutoff then probably not much crud would form.  If 2 stroke OPE then there may be a problem in one off season with the oil thickening or drying out. 

   If a damp place and the OPE with a shutoff then they could slid by for years without a starting problem. 

   From what I’ve seen it makes me think that having just one bowl full of gas evaporate probably would not be a problem and possibly a number evaporate and not be a problem. 

   Just to see what kind of buildup would form some jars were filled with gas and left to evaporate.  A few others were setup also with Stabil and SeaFoam just to see what would happen with them.

   The jars were left in an unheated mudroom so something like a garage or shed.

 From left to right. Water, SeaFoam, Stabil, SeaFrom and Gas, Stabil and gas, gas only, gas and water, gas SeaFrom and water, gas Stabil and water.  Two others not shown are SeaFrom and two stroke gas, Stabil and two stroke gas. 

   It's been a few weeks and they are evaporating down.  Their about 3/4's evaporated and no buildup in any jar.  The ones with water are sort of interesting so their posted below.

Gas and water.  Each jar with water got about 1/4 of a table spoon.  When the jar is shaken the water goes into the gas but blobs back up like olive oil in broth.  The gas is about 3/4 gone and the water seems the same as at the start.

 

Gas, SeaFoam and water.  The gas is about 3/4 evaporated.  The water at first blobed but over time would not go back to a big blob.  The white blobs have some body and although soft are much thicker than the gas.  A bit thicker and they would probably cause problems with the float needle and jet holes. 

Gas, Stabil and water.  The gas is about 3/4 evaporated and the water seems the same as at the start.  It goes back to a blob when shaken but does not go into the gas like at first.  At the start it would slightly cloud the gas slightly and slowly make smaller blobs that melded back to a big blob.  Not the big blob goes to much smaller blobs but does not go into the gas like before.  The amount of water seems the same as the start.

It seems if Stable or SeaFrom were added to gas and water got into the tank there would not be much protection.  These days with ethenol getting water in the gas over time is pretty likely.  That's not so much of a problem in the fuel bowl but is in the main tank.  It will blob up and be on the bottom and can make it down into the bowl where it will sit at the bottom there.  That could cause starting problems or if left long enough rusts the bowl causing pin holes.  If a machine is shaken the blobs will go into the gas and not be a problem for starting unless there is considerable water.  Given the above that would be ok unless SeaFoam was used. 

   Is a couple more weeks all the jars will be about done evaporating.  So far there is no noticable trace of any film buildup but they have been shaken occasionally so might be getting thicker and may be some film when they finally all evaporate. 

Nice experiment you got going there!  But aren't you afraid the evaporating gas will form an explosive atmosphere in the room?

I also think there's more to worry about than what's initially in the gas and is left when it evaporates in a few weeks.  Gasoline, over longer periods of time (months not weeks) will react with oxygen in the atmpsphere to form insoluble products (ie "varnish") that will cause problems with the carb.  How about trying the same experiment with sealed jars?  And maybe opening them briefly every week or so to replenish the oxygen.  And let it go all summer till fall and see what forms?

http://www.chemistryexplained.com/Fe-Ge/Gasoline.html

Here's a pretty good explanation of the air / gasoline process.  Interesting to note that traces of copper (as in brass carb components) accelerate the problem. 

Dr_Woof,

   You must not have read the post or skipped over:

 

->Leaving gas in OPE over the off season is often fingered as the culprit for varnish buildup.

 

->Just to see what kind of buildup would form some jars were filled with gas and left to evaporate.  A few others were setup also with Stabil and SeaFoam just to see what would happen with them.

 

->Their about 3/4's evaporated and no buildup in any jar.

 

->So far there is no noticable trace of any film buildup but they have been shaken occasionally so might be getting thicker and may be some film when they finally all evaporate.

Dr Woof: Gasoline, over longer periods of time (months not weeks)

   Months or weeks would depend on conditions. 

Dr Woof:How about trying the same experiment with sealed jars?

  A sealed container would not approximate a carb.  Carbs are not sealed they are vented.  Just how well depends on the carb.  There are other effects like carb design, closed/open butterfly, choke position, and valve position.  A machine left outside exposed to the wind, sun, versus inside or under a cover.  Lots of variables. 

   An open top jar would expose the gas to much more air than vent holes, emulsion tube and interior throat ports.  An open jar having more air does not replicate a carb and bowl exactly but the thought was it is roughly equivalent to the amount of air a carb would get over a long period. 

   The test is to see what buildup would happen over time with gas alone, gas with additives, gas and water with additives and to see if the additives alone would leave buildup.  So far it looks like the additives have not had much effect on getting rid of or neturalizing water.  SeaFoam even seems like a big negative with water. 

   In the past I've left Stabil in a cup and it evaporated to a pink film not unlike varnish it claims to inhibit.   By chance SeaFoam was left in a cup for a year and did not evaporate.  It acted something like a light weight oil and got thick.  So two jars got straight SeaFoam and Stabil to see just what they would leave. 

    By the way, the two jars not shown with 2 stroke gas are about 3/4's of the way evaporated.  It will probably take quite a long time for the oil to jell and harden.  Generally 4 stroke buildup takes longer than 2 stroke as the oil leaves such a thich layer blocking internal carb passageways.   

   As of today the only dry jar is the one with water only.  

  The gas only, gas Stabil, gas Seafoam , gas Stabil water, gas Seafoam water all have about 10-20 drops left of thickened deep orange amber liquid.   Given the color and amount it seems that they all have the remenants of gas.  

   The two stroke jars had gas, oil and Seafoam and Stabil.  Those have a deep blue liquid which seems to be the oil.  There's probalby some remenants of gas in there but indestinguishable becaue of the oil.  Given the amount it seems like most of the oil is still there so did not evaporate. 

    After 10 weeks the gas did not turn to varnish in any jar.  The jars were in a back entrance mudroom which is unheated and the temps ranging from freezing to 75 degrees with tthe average in the cooler range.

     If gas was left in the carb bowl, gas in the tank and no shutoff then what evaporated would have been replenished and just dilute the mildly thickened remanants.

     If gas was left in a bowl but the tank supply shutoff then on restart the gas shutoff would be opened and the new gas mixed with the partly evaporated gas making a burnable liquid.  No problems. 

    So it looks like leaving gas in for 2-3 months is not a problem with or without Stabil or Seafoam at least at these temps.  It might be different over the summer with temps averaging 70-80. 

    All in all I'm surprised that there were remenants of gas and none of the jars dried completely other than the water only jar.

    Both jars with Stabil and Seafram only evaporated to about half of their starting contents and not noticably thickened. 

    

  

Interesting experiment. Nothing to add, but it did make me think of a few things. (1.) Water. It seems to me water will sink to the bottom and be protected from air by the gas above it, until such time as the gas evaporates, then the water would evaporate. (2.) Ethanol fuel and water. Drygas is methanol. Does ethanol gas help to absorb water in the tank like methanol? If I had a source of pure gas I'd compare that with 10% with the same amount of water added to each. Then add drygas and see what happened. (3.) Stabil. Can't wait to see what happens to that. I know from experience that Stabil gets funky in the container if you don't use it fast enough - couple years.

Interesting experiment. Nothing to add, but it did make me think of a few things. (1.) Water. It seems to me water will sink to the bottom and be protected from air by the gas above it, until such time as the gas evaporates, then the water would evaporate. (2.) Ethanol fuel and water. Drygas is methanol. Does ethanol gas help to absorb water in the tank like methanol? If I had a source of pure gas I'd compare that with 10% with the same amount of water added to each. Then add drygas and see what happened. (3.) Stabil. Can't wait to see what happens to that. I know from experience that Stabil gets funky in the container if you don't use it fast enough - couple years.

 

   I thought they would all have dried up by now even with the cooler temps.  There have been enough hot days in the last month that also made me think the contents would have evaporated. 

 

>>Does ethanol gas help to absorb water in the tank like methanol?

   Not sure about the equality between the two but ethanol in an open container will absorb quite a bit of water given moisture in the air, enough in a quart to screw up starting.  Most people don’t let it hang around in open containers so not that much of a problem if someone is getting a few gallons and using it up. 

 

   Some stable I left in a container dried to a pinkish powder.  Some Seafoam left over stayed a liquid for almost a year, acted like an oil which I think it mostly is, a light oil of some sort something like Mystery Oi.

   As a note:  After working on about 200 machines over the last few years and the vast majority with starting problems I can't attribute one problem to Ethanol.  That is, problems related to degraded components from harmful effects of Ethanol.    

 

   As a note: Working of about 200 machines over the last few years and the vast majority with starting problems I can't attribute one problem related to Ethanol.