I saw the difference it made first hand. I knew I was going to need carb rebuilds, but I didn't know when I was going to be able to get it done. The boat sat there for a couple weeks then I put Stabil in the tank. I finally got them rebuilt 2 or so months later. The mechanic told me the boat would not start at all. They flushed the fuel out of the line and it was dirt brown. He also said it cleared right up in a minute. I never ran the motor after I put the Stabil in the tank. I was also told yesterday by the mechanic you need to run your motor for 5 minutes every two weeks. He said the fuel will evaporate out and the oil is what will varnish.