I'd use it in a mower or something with a carb thats easy to pull and clean,just in case it ends up being so stale it wont fire or fouls up the fuel system...water in the fuel is a good possibility from sitting,every time a can or tank warms up or cools off it sweats inside ,condensation gets into the fuel,next thing you know its only "half" gasoline and wont run a engine for beans,if at all..the problems it can cause will likely negate any "savings" by trying to run a vehicle with it..
I have used a lot of "old" gas when we got it free from cars being junked at the junkyard though,by putting it into a large barrel (we had those semi-transparent ones that used to hold fruit juice) and we'd let it sit at least a day before siphoning or pumping the gas out from the TOP of the barrel,to avoid getting the watery non-flamable stuff from the bottom that had settled out...
We still had to replace fuel filters every so often,despite having rigged up a water separator type filter to the pump we used to get gas from the barrel (much like a 6.2 diesel has factory on the early ones)...we didn't have much trouble running it in our carbed vehicles,but the fuel injected ones didn't seem so tolerable to the old fuel and the fuel filters seemed to clog up with water or dirt faster for some reason..we found the gas that sat the longest and stank the worst was often the stuff that caused the most problems,and just a few gallons of it could "poison" the whole 50 gallon barrel of "useable" gas,it had to be very diluted before it'd burn good in an engine.....if your gas smells rank or varnishy,I'd only use it to clean parts or start bonfires unless you like making a lot of work for yourself down the road..
Lawn mowers and small engines can run on some really rank gas OK,due to their low compression ratio,provided it still has enough "flamability"...but most of them suck to clean the carbs on nowadays,if you do try using it up that way I'd at least filter it well thru funnel with a dry cotton towel bunched up in it,that'll absorb most of the water and the bigger chunks of any dirt out..
If your gas has ethanol in it it'll keep any water in suspention rather than let it settle to the bottom,so its harder to tell if theres any water in it...until you try running something on it,then you'll know!..
--if it looks yellow or milky I'd say it'd be best not to use it to run anything..
