I have had good luck with a fuel additive they now sell @ West Marine called Star Tron; 3 ozs per 100 gallons your first time and 1.5 ozs after that and I have had good luck with it. A tugboat operator told me about it years ago when a small company in Chula Vista designed and manufactured it; and West Marine bought them out for the exclusive distribution. The bad thing about Biobor is the harmful stuff it attacks in your fuel turns hard and sticks to the side of your fuel tank white Startron thins it out and makes it stick in the filter.