Understanding the Motor Oil Additive Package

by Pete The Mechanic

You can never know enough in the automotive service business. Knowledge is truly power in our trade, now more than ever. Know the answers, and you're productive. Don't know the answers, and you wind up chasing your tail.

So what do you know about additives? Additives are to motor oil what knowledge and expertise are to automotive service personnel. They both help get the job done with less stress and better long-term results. But exactly what are motor oil additives? What do they do and how do they reduce motor oil stress? Let's find out.

What Are Motor Oil Additives?

Since the 1960s, special chemical brews called additives have been mixed into motor oil's base stock. These magical mixtures have substantially increased the motor oil's ability to lubricate, seal, cool, clean and protect engine parts from corrosion, and are responsible in part for the tighter tolerances, higher horsepower and lower emissions of today's engines. From one motor oil brand to another, the most important difference can be the additive package.

To unravel the mystery of additives and how they affect us, let's take a closer look at a six-pack of these individual chemical micro-brews. Extreme Pressure (EP) Additives

Often called anti-wear agents, these high-tech chemical cushions react with metal surfaces at frictional "hot spots" (such as cam lobes and valve stem tips) to form a protective chemical layer. Too much EP additive can cause chemical wear, or corrosion, while too little EP additive can cause mechanical wear, also known as scuffing. An engine's appetite for EP additives varies with driving conditions, engine design and oil consumption.

Oxidation Inhibitors

Sometimes called anti-oxidants, these chemical-reaction blockers keep atmospheric oxygen from mixing with motor oil. When oil gets hot, it naturally reacts with oxygen and gets thicker. Corrosive compounds can form within the oxidized oil and damage bearing metals such as lead, cadmium and copper. But anti-oxidants slow this process. Consumption of oxidation inhibitors varies with driving conditions, engine design, oil consumption and average oil level.

Detergents/Dispersants

Detergent/dispersant additives help keep the engine internals clean in two distinct ways. First, detergents prevent the formation of varnish and deposits on engine surfaces. Second, dispersants work with detergents to chemically suspend sludge particles and combustion by-products until they can be removed in the next oil change. The need for detergents or dispersants varies with vehicle mileage, driving conditions, engine design and oil consumption.

Rust & Corrosion Inhibitors

When water vapor and other by-products of combustion slip by the rings into the crankcase as "blow-by," they can combine to form powerful acids, which in turn can cause rust and corrosion. Rust- and corrosion-inhibiting additives act to prevent this deadly destruction by neutralizing the acids and surrounding corrosive molecules, isolating them from contact with metal parts in the engine. The requirement for rust and corrosion inhibitors depends on fuel composition, driving conditions, engine design and oil consumption.

Foam Inhibitors

Without foam inhibitors, moving parts in the engine could whip the oil into a foam, causing hydraulic lifter noise, improper lubrication and cooling, or worse, a loss of oil flow. Foam inhibitors work by weakening the surface tension of the oil, enabling any air bubbles that form in the oil to break the surface and escape. The amount of "head" on a glass of beer is partly determined by the surface tension of the beer. Typical consumption of foam inhibitors varies with driving conditions and engine design.

Pour-Point Depressants

Pour-point-depressing additives function like anti-freeze for the oil. When oil gets very cold, wax deposits in the base oil stock can crystallize. If these crystals grow, the oil will become too thick for use. Pour-point depressants chemically coat the wax crystals, preventing their growth. An engine's need for pour-point depressants varies mostly with driving conditions (temperature) and engine design.

Stress Prevention Techniques

Usually when you have a stressful day at the shop, it is from a combination of factors, not just one bad occurrence. Mr. Quick's part is not in stock...anywhere. Ms. Persnickity's engine misfire is very intermittent. Two technicians and one service advisor are out sick. And to top it off, the air compressor just died. Darn! That's stressful.

Situations such as these are pretty much out of our control. An effective way to reduce stress, however, is to improve things that are within our control. One thing we are in control of is our level of expertise and know-ledge. All other things being equal, if service person A knows more than service person B, then service person A will be able to handle his/her job better and with less stress.

Motor oil can be the same way. All other things being equal, if motor oil A has a better additive package than motor oil B, then motor oil A will be able to handle its job better and with less stress.

We're The Automotive Systems Analysts

Our customers look to us to know their vehicles' various systems and how they operate. The oiling system is no exception: it is the lifeblood of the engine. I hope this information adds to your ever-growing base of automotive technical knowledge and helps you to explain motor oil's im-portance to your customers. Heck, maybe it'll reduce your stress level.

Pete Sullivan is a technician and owner of Sullivan's Advanced Auto Care in Houston, Texas. He is a triple master certified by the National Institute of Automotive Service Excellence (ASE). He holds a B.S. degree in Physics and Chemistry.