This will be the first year that I did not top off my tanks; I was always a believer on doing this till recently. After extensive research I found a site that discussed modern day gas and gas of the 60s and 70s era. In a nut shell, gas today has a very short shelf life, this site said 30 days before the octane starts to go south. Funny thing, after I read that I remembered a friend of mine that owns a Mobil gas station telling me that when he renovated his station, Mobil would not let him sell the gas in his tanks because it would be sitting there for more than 30 days.
As far as water condensation, another site I visited explained the math of this and how much water could actually exist due to condensation. Based on my tanks (142 gallons each) with the worst conditions and the tanks bone dry, I could only see an ounce or two of water.
I left my tanks half full this year and will either add an octane booster or top them off next season with high test. I have that MPI fuel injection system in my boat, this system automatically adjusts the motors(timing) to run better if there is less octane than needed (my octane is 87). Reason I mention this is that you may not notice a difference in the spring because your motors are compensating for the lower octane. You will burn more fuel and I am not sure if it is bad for your motor.
If you have carburetors and run the boat with low octane you will here the motors ping and you will definitely be doing damage if you do not add an octane booster, top off with high test or retard your timing till you burn the gas off.
As far as fuel stabilizer, I still use it but have no other reason to tell you other than I always have. My understanding is it prevents the gas from gumming up.
PS.
If I have any problems next season I will be deleting this post.
Walter
