I have some old 2 stroke mixed gas I need to get rid of. This could also apply to old fuel removed from a sitting car or any vehicle for that matter. What is the proper way to dispose of this? Are recycling centers common? I think once in the past, I gave some to an auto repair shop and they just put it in their oil/gas burner heater.
Depending on how old it is (<1 year for me) i have always just mixed it with fresh fuel and used it like normal. No problems. Fuel older than a year makes a great grease cutter, it does a great job at loosening up bolts, old parts, and grease and crud off of skin.
Be sure not to use in enclosed spaces, only recommended to use outdoors.
So long as it is clean and just old, put it in your nearly full car tank. A small amount of 2-cycle oil will not matter diluted from say 50:1 to say 2500:1. In driving 5000Km you might use 500L of fuel and perhaps 0.25L of engine oil. That's a ratio of 2000:1, so adding a bit of 2-stroke mix won't harm unless the 2-cycle oil used is particularly bad for your catalytic converter.
Even if your car uses diesel, a 2% gasoline mix will do no harm. VW used to recommend a 25% gasoline mix to stop the diesel freezing in the Canadian winter.