Re: Old fuel
Here are a couple of basics:
You can't add startron, etc. to bad gas to make it better. The additives only preserve the gas in its present state--for a while.
I don't believe that the treatments like startron will be effective after three years, or even two. It's my impression that it's intended to work for several months, like over winter.
Mixing bad gas with good, such as on a 25%/75% ratio, can work but not if the old gas has water in it, including water produced from phase seperation, condensation and other E-10 issues.
Bad gas affects small and delicate engines--which includes lawn equipment. A tractor or 1980's vintage F150 can handle it. A computerized injection system in a car might not and the risk is an expensive repair. But the risk of a big expense from running bad gas through an old lawnmower is not as high, so some people chance it. And a lawn mower that isn't running well isn't far off from one that is.
"Lawnmower gas" goes bad, too, especially if it's E-10. If you don't use it all in a month or two, put it in your car* and get fresh. So don't use 2 year old gas in your lawn mower, whether it comes from the boat or the can in the garage.
Cars don't usually have the same problem because the gas is used within a month and there is usually less exposure to moist air in the tank.
*The advice to put it in your car sounds contrary to the above but here is the thinking: You dillute the stale gas (1 gallon) with a fresh tank (20 gallons) and you will use it all up in a week or so. This is not the same as several gallons at a time or two year old gas.
Some parts of the country don't experience the problem as much as others--this is a factor of temperature swings, high temps and high humidity. The guy in Minnesota can use year old gas all the time with no problem; the guy in Florida may have a problem with 6 month old gas.
Oil companies often do salvage/clean up work and they can take in your bad fuel, for a fee. You can even trailer your boat full of bad gas to them and they will suck it out. Some companies can come to your boat, clean and return the gas to your tank. City hazmat disposals often limit the number of gallons you can bring in.
