Some fuels will leave deposits and some are more corrosive than others (i.e. Nutec). U4 will offer more of a performance increase on the modern higher revving 4 strokes (CRF250, CRF450, YZF/WRF, etc) than it will on our slow running torque monters. As far as I know, U4 doesn't leave deposits like some of the other fuels, but you must keep it sealed in a Air Tight Metal container or else you'll loose what you're paying for (more performance). It definitely has an odor to it The shelf life of U4 in a sealed metal container is ~5 to ~9 months from what I recall, but only 5 hours in a plastic container in the shade and just a mere ~45 minutes in the sun U4 is good stuff, but per comments from Honda's Bruce Ogilvie... "A stock XR650 will run better on pump gas than a high-octane race fuel, which needs a higher com*pression ratio to be effective. (All gas in the Honda pits is Chevron 92- or VP 93-octane unleaded.) "