Use of additives is another approach to improving and maintaining oil performance. High engine temperatures combine with moisture, combustion byproducts (including unburned gasoline), rust, corrosion, engine wear particles and oxygen to produce sludge and varnish. The additives not only assist oil in maintaining good lubrication, they also help minimize sludge and varnish, and any damage from their formation. Here are the categories of key additive ingredients and why they're important:

• Viscosity-index improvers: Reduce the oil's tendency to thin with increasing temperature.
• Detergents: Unlike the household type, they don't scrub engine surfaces. They do remove some deposits, primarily solids. But their main purpose is to keep the surfaces clean by inhibiting the formation of high-temperature deposits, rust and corrosion.
• Dispersants: Disperse solid particles, keeping them in solution, so they don't come together to form sludge, varnish and acids. Some additives work both as detergents and dispersants.
• Antiwear agents: There are times when the lubricating film breaks down, so the antiwear agents have to protect the metal surfaces. A zinc and phosphorus compound called ZDDP is a long-used favorite, along with other phosphorus (and sulphur) compounds. If you musts know, ZDDP stand for zinc diakyl dithiophosphate.
• Friction modifiers: These aren't the same as antiwear agents. They reduce engine friction and, so, can improve fuel economy. Graphite, molybdenum and other compounds are used.
• Pour-point depressants: Just because the 0А F viscosity rating is low doesn't mean the oil will flow readily at low temperatures. Oil contains wax particles that can congeal and reduce flow, so these additives are used to prevent it.
• Antioxidants: With engine temperatures being pushed up for better emissions control, the antioxidants are needed to prevent oxidation (and, therefore, thickening) of oil. Some of the additives that perform other functions also serve this purpose, such as the antiwear agents.
• Foam inhibitors: The crankshaft whipping through the oil in the pan causes foaming. Oil foam is not as effective a lubricant as a full-liquid stream, so the inhibitors are used to cause the foam bubbles to collapse.
• Rust/corrosion inhibitors: Protect metal parts from acids and moisture.

More Is Not Better

You can't necessarily improve an oil by putting in more additives. In fact, you can make things worse. For example, sulphur compounds have antiwear, antioxidation characteristics, but they can reduce fuel economy and affect catalytic converter operation. Too much of a particular detergent could affect the antiwear balance. Too much of a specific dispersant could affect catalyst performance and reduce fuel economy. Antiwear and friction-reducing additives also may have ingredients (such as sulphur) that could affect catalyst performance.
There's a lot of pressure on the oil industry to reduce sulphur content in oil as well as gasoline. But the industry's resistance is understandable when you consider the delicate balancing act it must perform with each revolution of your car's engine.

Time for lab testing our oil blend. This machine draws oil from the beaker and runs it through the Lawler equipment on the right. In there, the oil is chilled to measure its low-temperature viscosity performance.

Coefficient of friction: A sample of our custom-blend oil is placed on a flat plate on this machine. A ball is placed on the plate and a weighted cover goes over the ball. The machine then starts vibrating while measuring current draw. The amount of current varies according to the friction between the ball and plate, and this is converted to a coefficient of friction number for the oil sample.

Here are the little ball and plate used for coefficient of friction measurement.