I've got about 10 gallons of 2 year old gas in my Cuda. I put fuel stabilizer in when tank was full and then threw a little more in last summer when I realized I wouldn't be driving car last year.
Should I just top it off to dilute the old gas? Or, siphon tank dry and refill with fresh gas?

What does old gas do to an engine exactly, if anything? I did start the car for a minute and it started right up and idled smoothly. Didn't drive it though.