I'm not sure if this is the correct forum for this question.
I have some 40:1 mixed gas (for my snowblower) that is about 6 month old with no stabilizer added. I haven't t tried it yet but should it be okay to use or should I start with new?
I think you could very well be ok. I think some mitigating circumstances are these surround if the gasoline was extremely hot repeatedly. Sitting outside in the sun every day would qualify. The heat would break down your fuel a bit every day.
If the fuel smells bad and doesn't smell like gasoline, you could have bad gas.
If you did, you can try draining it and then refill and start.
If it became gummed up, which I doubt, you probably need to remove the carb and thoroughly clean it with carb cleaner and, hopefully, compressed air.
If it's running a bit choppy and actually starts you can put some alcohol in it to get any water in the fuel to mix into the gas and/or you can put a bit of seafoam in the gastank that would clean out the internals of your carb and your combustion chamber.
I would say, give it a try and if it doesn't work, come back with the symptoms for a more detailed response on some action items to get it up and adam again.
Hope this helpful.