Red Line SI-1 Complete Fuel System Cleaner (15 oz.)

Dirty injectors rob your engine of fuel economy and throttle response, and Red Line's SI-1 is one of the most concentrated detergent-based cleaners you can pour into a tank. Red Line SI-1 Complete Fuel System Cleaner works through the entire fuel path — injectors, intake valves, pollution control valves, and combustion chambers — using high-temperature detergents that break down deposits where they form.

One 15 oz bottle treats a full tank and can clean injectors to near-full efficiency in a single use. Red Line notes that heavily fouled injectors can see fuel economy improvements of around 12 percent once deposits are cleared, and octane requirements may drop by up to two points. The formula also includes a synthetic upper-cylinder lubricant that conditions valve seats and reduces wear in the upper end of the engine. SI-1 is safe for continual use with oxygenated fuels, and smaller doses work well for maintenance between deeper treatments.

Worth noting: SI-1 is a gasoline-only product and is not intended for diesel engines. If your fuel system has gone a long time between cleanings, a full-dose treatment followed by a lighter maintenance dose every few fill-ups is a solid approach.