If it truly is 15 bucs a quart I'd use something else. Maybe 50 bucs a gallon? Anyway, Star Tron is a great substitute and I notice it's sold right next to the Yamaha Ring Seal here at my Yamaha dealer. I was having to go just about every year for carburetor cleaning till I switched to Star Tron. First time I used it I noticed smother running and seem to feel more power out of my 50 horse two stroke. Using it for two years now. It's not cheap but it's not 50 bux a quart. More like 10 bux a pint but don't have to use much. An oz. for every 8 gallons as I recall.