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.
