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Gas additives keep your engine clean and mean

We regularly get questions about what gas to use–an important question not only from the standpoint of savings but also for engine health. All gasoline is created equal, or at least nearly equal. From refineries around the country, gasoline is shipped via pipeline to where it is stored in “tank farms”—-vast lots with numerous huge tanks dotting them like giant checkers on a board.

It is at this point that gasoline marketers add their secret blend of fuel additives before shipping the fuel to the retail stations.The main reason for those additives is to keep the fuel-delivery systems in our vehicles clean. With insufficient additives, fuel injectors get plugged up, intake valves get dirty and combustion chambers develop buildups of carbon. The most important are detergents and dispersants. These additives keep the fuel injectors clean. Without sufficient additives, the injectors can suffer varnish buildup. The injectors need not fully clog to cause problems. Even a little buildup can cause drivability problems. The tiny hole in the injector’s tip can become restricted, creating a poor spray pattern. Varnish in the injector can prevent it from fully closing, allowing it to dribble.

Because the fuel system stays pressurized after your turn off the engine, a dribbling injector can allow gasoline to puddle, causing flooding and hard starting. This is especially troublesome in short hot-soak periods such as when you go to the store.

Some low-quality detergents cause deposits to form on the backs of the intake valves. Most injectors are aimed at the valves so the atomized gasoline can readily mix with the rush of air on it way to the combustion chamber.

This blackish buildup on the valves is not a solid, but porous. It’s more like a sponge or piece of lava.

On a cold engine, this spongy buildup absorbs the gasoline before it gets into the combustion chamber. Just when the engine needs extra fuel for a cold start, there is less of it to burn. Once the valve buildup becomes saturated and the engine reaches normal temperature, the drivability problem goes away because the sponge is full and no longer absorbing the gas.

Insufficient additives also allow buildups in the combustion chambers. This reduces the chamber volume, which increases compression, which leads to engine knock. Higher octane fuels resist knock and that is one reason we recommend an occasional tankful.

Though it’s best to use gasoline of the octane recommended in your owner’s manual, premium grade gasolines from reputable marketers have the most and better (more expensive) additives. That’s another reason we suggest an occasional fill-up with premium–especially for those who routinely shop for the lowest priced gas. It can help keep your injectors, valves and combustion chambers clean. The other option is occasional use of a fuel additive.

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Bob Weber is an ASE-certified Master Automobile Technician, having recertified every five years since 1978. Contact him at motormouth(underscore)trib@verizon.net.