The 10 Best Fuel System Cleaners

For most gas cars, Chevron Techron Concentrate Plus is the simplest place to start. It's built on a heavy-duty detergent that keeps working in the hottest parts of the engine, where carbon bakes onto injectors and valves. One bottle doses a tank of up to 20 gallons, and Chevron says it also keeps stored fuel fresh for up to a year. It won't rescue a badly clogged injector, and the bottle can leak if it rides on its side.

For a strong one-time cleanup, look at Red Line SI-1. Red Line pairs a concentrated detergent with a synthetic lubricant for the tops of the cylinders, and its spec sheet calls it safe for oxygen sensors and catalytic converters. For a deep clean, pour the whole bottle into a nearly empty tank, then fill up. For upkeep, half a bottle every 1,500 miles does the job. The full dose makes it a pricey habit for every tank.

BG sells BG 44K Platinum mainly through repair shops, and the label says it's meant for professional use, though anyone can buy a bottle. A full bottle suits a tank of about 13 to 20 gallons, and BG gives smaller pours for smaller tanks. It goes after deposits on injectors and intake valves and in the combustion chamber. It's one of the costlier bottles to use often, and BG shares little test data with buyers.

Liqui Moly Pro-Line is the workshop-strength gas cleaner from a German oil company, and it comes in a metal can with a long spout that reaches past tight filler necks. One can treats a tank of up to about 18 gallons. Liqui Moly aims it at gummed-up injectors, intake valves and carbon in the combustion chamber. It's pricey per dose, and the can carries a California chemical warning.

Cars past 75,000 miles are the target for Gumout High Mileage, which comes as a multipack of small bottles, one per fill-up. Gumout says the formula is built to break down the hard carbon that piles up in older engines, and that it's safe for oxygen sensors and turbochargers. Nothing needs measuring. Each one holds a light dose, so it's better at keeping deposits away than at clearing a stubborn clog.

Meant for every fill-up rather than an occasional shock dose, Sta-Bil In-Season Protection adds a small measured shot of detergent to each tank. The jug has a built-in measuring chamber, and it treats up to 160 gallons in all, so one lasts a long while. It also guards against moisture and corrosion from ethanol blends. Sta-Bil sold the same formula as 360 Protection before a rename. The low dose won't clear heavy buildup; it keeps a clean engine clean.

Sea Foam has sold Sea Foam Motor Treatment since the 1940s, and it goes in gas or diesel, in the tank or the crankcase. It's a petroleum solvent blend rather than a detergent concentrate, so it shines at loosening gum and varnish in carburetors, mowers and engines that sat too long. It also helps stored fuel last. It's highly flammable, the recommended dose is generous, and the link here is for a four-pack.

Think of the Lucas Oil Renewal Kit as a four-tank plan: a stronger cleaner for the first fill-up, then a lubricant with injector cleaner for each of the next three. It works in gas or diesel engines, carbureted or injected, so one box can serve a household with a truck and a car. The small bottles don't need measuring. Lucas publishes little on how much it removes, so expect upkeep rather than a cure.

From the synthetic-oil company, Royal Purple Max-Clean does two jobs: it cleans with a concentrated detergent and keeps fuel from going stale in storage. Royal Purple claims small gains in mileage and power from its own testing, not from an outside lab. It suits a weekend car that sits between drives. It comes as a two-pack here, so the first purchase is steep.

Boats, mowers and anything that sits for months are the target for Star Brite Star Tron, an enzyme fuel treatment rather than a classic injector cleaner. Star Brite says it keeps ethanol-blended gas from separating with water and keeps fuel usable for up to two years. A capful covers a mower-size tank, and one jug goes a very long way. Don't expect it to clear carbon from a daily driver's injectors; that isn't its job.