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Do Additives Really Work?

by Grassroots Motorsports

Posted on 12/4/2024 at 9:00 AM

Pouring oil to engine



You’ve seen them: rows upon rows of brightly colored bottles, each promising more than the last. Improved fuel economy! Cleaner engine internals! A full head of hair!

Yes, we’re talking about fuel additives. What exactly is in those concoctions? The answer can vary greatly. In theory the safety data sheet, usually available online, spells out their contents–helpful info should there be some kind of an incident. Sometimes, though, the SDS just provides a possible range of concentrations for individual ingredients.

For a real-world example, let’s take a closer look at a popular additive that promises a cleaner, better-performing engine. (We won’t name it, but let’s say it’s one that has been promoted for decades.) 

The SDS lists kerosene among its ingredients. The kicker: According to the SDS, the amount can range from 15 to 97 percent. Similar huge ranges are provided for several other additive ingredients. Kerosene, which is often used in fuel additives as a filler or carrier for the active ingredients, isn’t the worst thing to feed an engine, explains Zachary J. Santner, senior specialist of quality at Sunoco. “Kerosene is a really good solvent,” he explains, “and it’s relatively safe as far as bottling it and putting it in stores.”

Thanks to the vague information found on the SDS, however, exactly what is being fed to the engine remains a mystery. The bottle might contain all active ingredients, or it might be mostly filler.

For those who feel the need to use these aftermarket additives, Santner recommends following the directions on the bottle. Too much solvent can be harsh on gaskets or other internal components. “If one is good, two isn’t always better,” he adds.

How can you keep your engine clean in the first place? Using a Top Tier Detergent Gasoline can certainly help, he says. This standard was unveiled in 2004 so auto manufacturers could easily specify a fuel deemed clean enough for use in their engines.

More information on Top Tier Detergent Gasolines can be found at, and Santner notes that all Sunoco products are on that list–all grades, all stations, all seasons. (Something that we noticed: Offering clean restrooms and artisan sandwiches doesn’t guarantee a spot on this list.)