Quite often the subject of motor oil comes up during my radio program. Questions such as: How often should I change the oil? What type of oil should I use? What kinds of oils are available? What do the letters and symbols on an oilcan mean?

Before I answer these "Frequently Asked Questions," allow me to preface with my basic philosophy on changing oil.

The single most important thing you can do to get long life from an engine is to change the oil at least as often as your car's manual or Oil Life Monitor indicates. Most manuals suggest changing the oil every 3,000 miles if the car is driven under severe conditions. Many people are not aware of the fact that severe conditions include 'driving around town.' Stop-and-go driving is far tougher on the engine than highway driving. Check your owner's manual. It probably lists this type of driving as 'severe service'(unless you have a new GM vehicle, then you follow the Oil Life Monitor system). Other kinds of severe service include:

  • Making frequent short trips (less than five miles)
  • Making frequent short trips (less than ten miles) when temperatures are below freezing
  • Driving in stop-and-go traffic during hot weather
  • Driving at low speeds for long period of times (like in heavy traffic)
  • Driving at sustained high speeds during hot weather (interstate driving)
  • Towing a trailer
  • Driving in areas with heavy dust and gravel (example: highway construction)

All these service descriptions can cause engines to become severely overloaded and develop very high engine and oil temperatures, resulting in viscosity breakdown and ultimately engine damage. Correct me if I'm wrong, but don't we all drive under one or more of these conditions all year 'round? THIS IS WHY it makes sense to change your oil every 3,000 miles or 3 months, whichever comes first! Now let's get to the FAQ's.

What types of motor oil are available?

There are three types or blends of motor oil on the market:

1. Natural: The best known is what you might call "conventional" oil. This mineral oil originates deep underground and is pumped out as crude oil. It is then refined to improve its performance. Additives such as detergents, viscosity (flow) improvers, anti-wear agents, and inhibitors of corrosion oxidation and foam are blended in.

2. Synthetic: Synthetic oil is quite different. It's a man-made lubricant. Oils like this were originally created for jet aircraft engines. They have such a wide range of performance that they can protect engines at temperatures so cold ordinary oil would turn to jelly, or so hot that conventional oil would break down. In engineering terms, they have exceptional 'thermal stability.'

3. Synthetic/Natural Blends: The third type is a combination of mineral and synthetic oil and can offer the benefits of both types of oil. It has the full body of petroleum based oil and the flow-ability and toughness of synthetic oil. This kind of oil is becoming increasingly popular for cars and trucks that undergo 'severe service.' These include high-performance cars, vehicles that haul trailers or carry heavy loads, or sport utility vehicles that not only do this kind of work, but spend part of their lives off-road.

What do the letters and symbols mean on the bottle, such as API, SJ, CF, CG-4? Or SAE 5W-30?

API stands for the American Petroleum Institute, which provides the standards that high quality oils must meet.

SL is for all automotive engines presently in use. SL oils are designed to provide better high temperature deposit control and lower oil consumption.

SJ is for 2001 and older automotive engines.

CF was adopted in 1994 for use in indirect injected off-road diesel engines that use a broad range of fuels, including those with a high sulfur content. It offers effective control of piston deposits, wear and corrosion of the copper-coated bearings used in this type of engine.

CF-2 is formulated for use in two-stroke diesel engines requiring highly effective control over cylinder and ring-face scuffing and deposits.

CF-4 covers oils for use in high-speed, four-stroke diesel engines. They are designed for use in on-highway heavy-duty truck applications.

CG-4 describes oils for use in high-speed, four-stroke diesel engines, and is suitable for both highway and off-road applications. They provide effective control of high temperature piston deposits, wear, corrosion, foaming, and oxidation stability and soot accumulation. These oils are especially effective in engines required to meet 1994 emission standards.

CH-4 was introduced December 1, 1998. This oil is for use in high speed four stroke engines designed to meet 1998 exhaust emission standards. CH-4 oils are specifically compounded for use with diesel fuels ranging in sulfur content up to 0.5% weight. It can be used in place of CD; CE; CF-4 and CG-4 oils.

SAE stands for Society of Automotive Engineers. Motor oils have SAE grades, or numbers that indicate viscosity. In other words, the SAE numbers tell you the "thickness" of the oil. The lower the number, the "thinner" the oil.

W signifies its winter rating, showing that it will perform well in particularly cold weather. What does a viscosity rating of 5W-30 mean? The number and letter designation signifies the winter flow weight of the oil. Colder temperatures tend to thicken oil so that it flows very slowly. This is disastrous to your car's engine. Therefore, in mixing the oil, the refinery adds a chemical (or package) that adjusts and stabilizes the oil at the lighter weight when it gets cold outside. Consequently, it will flow more easily and freely (necessary for lubrication of the engine) at sub-zero temperatures. The higher number at the end of the viscosity rating signifies the weight the oil adjusts to, at higher temperatures. High temperature tends to break oil down and affects its lubricating ability. Therefore, the refinery adds a package that toughens the oil to stand up and maintain enough body in order to perform its job at high operating temperatures.

When you buy oil (or have it changed), make sure you pick the right API rating for your engine, and also ask for the SAE viscosity recommended in your owner's manual. Car manufacturers recommend multi-viscosity grades, which are suitable for use over a wide temperature range. Automobile manufacturers specify the proper SAE viscosity rating in your owner's manual. Multi viscosity oils provide excellent protection in virtually all parts of the US. SAE viscosity rating becomes especially important when you take into consideration the vehicle's warranty. You cannot hold a manufacturer accountable if your car's engine seized up at 25,000 miles because you used the wrong oil. Using the wrong oil voids the warranty!!! So save yourself a major headache and financial woes and follow your owner's manual.

'Til next time ... Keep Rollin'

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