The 10 Best Diesel Additives

If you want one bottle for every season, the Stanadyne Performance Formula is the safe bet. Stanadyne builds diesel fuel pumps, and this blend raises cetane, cleans injectors, adds lubricity and helps fuel keep flowing in the cold. Several big truck and engine makers have approved it, and the label says it's safe for modern exhaust filters and biodiesel blends. The plain jug has no measuring neck, so small tanks need a cup.

Cummins endorses the Power Service Diesel Kleen, a year-round treatment that suits most trucks. It cleans injectors, including modern high-pressure types, adds lubricity for today's low-sulfur fuel and raises cetane by up to six numbers. Power Service says it won't harm late-model exhaust systems or void an engine warranty when used as directed. It does nothing to stop gelling, so it needs a separate anti-gel once nights drop below about 30 degrees.

Small bottle, simple routine: the Hot Shot's Secret EDT is meant for every fill-up, and a built-in measuring chamber makes dosing quick and clean. One ounce treats about 25 gallons. Hot Shot's says it raises cetane by up to seven points, adds lubricity, cleans injectors and helps disperse small amounts of water, and a double dose is allowed for more boost. A bottle runs out fast on a big truck, and it won't stop winter gelling.

Owners of late-model trucks with soot filters are the people the Archoil AR6500 is aimed at. Archoil says it cuts pump wear by more than 40 percent in the standard lubricity test, raises cetane by up to eight points and slows soot buildup in the filter and turbo, which can mean fewer cleaning cycles. A long neck reaches capless filler openings. Every figure comes from the maker's own testing, and the bottle costs a lot up front.

Built for drivers who worry most about fuel-pump wear, the Opti-Lube XPD puts lubricity first and adds injector cleaners, a water separator and stabilizers that the maker says double storage life. It doubles as an anti-gel in cold weather at a heavier dose, so one jug covers the whole year. Common-rail pickup owners bring it up again and again on diesel forums. The gallon jug is a big buy at once and awkward to pour without a pump.

When an engine smokes, idles rough or has sat for months, the Hot Shot's Secret Diesel Extreme works as a strong cleaning dose rather than a daily habit. It's made to clear deposits from injectors and the tank, pull out free water, stabilize fuel and add some cetane and lubricity. Hot Shot's says it can cut soot-filter cleaning cycles too. The dose is heavy, so one jug covers only a few fill-ups on a large truck.

Gelled fuel is the classic winter breakdown for diesel owners, and the Power Service Diesel Fuel Supplement is made to prevent it. Poured in before the cold arrives, it keeps wax crystals from clogging the filter, stops filter icing and adds cetane and lubricity. Power Service says to start using it below about 30 degrees and to double the dose in deep cold or with biodiesel. It can't rescue fuel that has already gelled.

For fuel that sits in a generator, tractor or backup tank, the Sta-Bil Diesel Fuel Stabilizer slows the breakdown that turns old diesel into sludge. It also helps clear water, guards metal parts against corrosion and works with low-sulfur fuel and biodiesel blends. A measuring chamber on the bottle makes small doses simple. Once it's opened, use it within about two years, and know that it doesn't kill microbes already growing in a tank.

Dark slime in a fuel filter usually means bacteria or fungi are living where water meets fuel, and the Biobor JF is a biocide that kills them. Hammonds has sold it since 1965, and it's a common choice for boats, farm tanks, heating oil and aircraft. It adds some lubricity too. It's a pesticide, so follow the label closely, including the stronger shock dose for a tank that's already contaminated. It won't remove water or clean injectors.

An old standby for mixed garages, the Lucas Oil Fuel Treatment goes in gasoline and diesel engines alike. It's mostly a lubricant for the fuel pump and upper engine, with injector cleaners blended in, and Lucas says it suits low-sulfur fuel. A dosing scale is printed on the side of the quart bottle, so measuring is simple. It does nothing for cetane or cold weather, and Lucas publishes little detail about diesel use.