Do Motor Oil Additives Work?

oil containers on the shelf

What do motor oil additives do?

The shelves at your local auto parts store are full of aftermarket motor oil additives and oil treatments that promise a cornucopia of benefits, such as…

  • Increased fuel economy
  • Reduced friction
  • Maximum horsepower
  • Improved engine cleanliness

To provide this added performance, aftermarket motor oil additives use different chemical components to augment the motor oil formula. Some products have advertised materials like Teflon, molybdenum or graphite. Some have used chlorine, which can be highly corrosive when mixed with water.

Should you use motor oil additives?

The fact is, motor oil must fulfill several responsibilities. While wear protection is top-of-mind for most motorists, your motor oil must also…

  • Help keep engine parts clean by holding contaminants in suspension so they don’t form harmful deposits on metal surfaces
  • Cool engine parts by absorbing heat and carrying it to a place where it can be safely dissipated, such as an oil cooler or the oil pan
  • Act as a dynamic seal to minimize combustion by-products from contaminating the lubricating system, such as the piston ring/cylinder wall interface
  • Dampen shock to help protect against wear
  • Prevent corrosion to engine parts by chemically neutralizing corrosive products or setting up a barrier between the components and the corrosive material
  • Transfer energy, such as in the case of hydraulic equipment or valve lifters in an automotive engine

The chemists and engineers at motor oil companies work hard to fine-tune their formulations to fulfill all the requirements of a motor oil. While aftermarket additives may claim to boost performance in one or two areas, they can’t hit them all.

What’s more, aftermarket oil additives are not necessary in fully formulated oils. High-quality engine oils are blended with additives that are carefully balanced to be synergistic, performing well together.

Take a motor oil formulated for today’s advanced engines, like a turbocharged, direct-injection model. The oil not only has to fight wear, it must stand up to the intense heat generated by the turbo, maintain protection despite potential fuel dilution reducing oil viscosity, combat low-speed pre-ignition in some cases and maximize fuel economy. And it must do it throughout today’s longer oil-change intervals without missing a beat.

Modern oils, in essence, are nearly as sophisticated as the engines in which they’re used. Tampering with the balance by adding other chemicals can adversely affect overall oil performance, sometimes dramatically.

Buyer beware

The decision to use aftermarket additives is ultimately yours to make, but be wary of performance claims. Some additive manufacturers have been charged by the FTC with making false claims in the past.

For the record, AMSOIL recommends against using aftermarket additives. AMSOIL synthetic motor oils are fully formulated to provide superior protection and performance; use of aftermarket additives will detract from their performance and possibly lead to engine failure. Use of aftermarket oil additives not approved by AMSOIL INC. will void the AMSOIL Limited Warranty.


  1. Has Amsoil completed any testing on adverse side affects of residual motor oil interaction with new oil. Example would be oil that has started to breakdown, fall out of viscosity, become contaminated with wear metals, fuel or other harmful by-products, and may contain binding agents, additives of varying quantities and quality that may not be compatible with Amsoil and cause inbalances in Amsoil’s formulation. In modern engines up to 20% of the residual old oil will remain in the engine. I agree that mixing oils and using aftermarket is not recommended. When starting out with Amsoil, would you recommend a Full Volume Oil Change.

    1. Hi Brian,

      We perform extensive testing to ensure compatibility with aged/depleted oil as well as with other oil brands (conventional and synthetic). While some residual oil remains after a drain, additive levels are restored with each oil change. Also, using a high-quality synthetic reduces breakdown from shear, fuel dilution or heat/oxidation. Using a high-efficiency oil filter also traps metal particles/soot agglomeration large enough to cause wear. We recommend a standard drain-and-fill process (with filter change) when switching. No special procedure is needed.



    1. Hi Scott,

      We don’t recommend using any aftermarket additives with AMSOIL synthetic motor oils. Oil additives can disrupt the chemistry of the oil and reduce performance or service life.



  2. Thank your for sharing such a nice article regarding the important role of motor oil. It reduces the friction among the different components of the engine and hence ensures smoother performance and increases the fuel economy of the vehicle. Apart from this, it also absorbs certain amount of heat generated by the engine and provides optimum temperature to the engine. However, it degrades with the flow of time due to the extreme heat generated by the engine and needs to be replaced with suitable alternatives according to the manufacturer’s recommendation. However, some people underestimates the importance of oil change after certain interval in order to ensure smoother performance for a relatively longer periods.

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