Lifter noise in an engine can be caused by a variety of problems including age, damage, wear and tear, and dirt or debris. Additives will not change the amount of wear that your engine has experienced if you have driven it many miles or damaged it, but there are several products that you may be able to use to reduce the amount of noise coming from your engine's lifters.
If the noise in your lifters is being caused by trapped debris inside your engine, flushing it with a cleaning product that has been specifically designed for engines may help remove the dirt. Engine flushes are designed to remove built up gunk, dirt and debris that may be causing it to run poorly or stopping oil from lubricating the engine efficiently. A lack of lubricant is often responsible for the knocking or tapping noises you may be hearing from your engine. However, it is possible that the engine flush can cause other problems due to the debris breaking apart and clogging other components. Engine flushes should only be performed by certified mechanics who are willing to warranty their work.
High Quality Oil
Some oils are designed to provide better lubrication than others. While fully synthetic oils can possibly improve fuel mileage, it has been reported that semi-synthetic oils will provide your vehicle's engine with better protection against the knocking and tapping caused by a lack of lubrication. A thicker viscosity oil may also help reduce lifter noise, as can an oil designed for use in engines with high mileage.
There are a wide variety of products on the market that claim to be able to reduce wear and extend engine life. These products combine the detergent and cleaning quality of engine flushes with a dosage of extremely thick engine lubricant. They are typically sold in very small amounts that can be added, a couple ounces at a time, to your vehicle's engine oil. Though these products claim to perform a variety of tasks which may benefit your engine and reduce the amount of noise coming from you lifters, depending on what the lifter noise is being caused by in the first place, there is no guarantee that any one of them will work on your particular vehicle.