Journal-News

Wheels: Last week you discussed viscosity rating. Is there anything to add to that?

Halderman: Many readers have written saying that they are concerned about using thin (low-viscosity) oils. The low viscosity oils can be pumped by the oil pump inside the engine much faster than a thicker (high-viscosity) oil. A thinner oil also allows the engine to produce more power and helps improve fuel economy.

Wheels: What other specifications should readers look for when purchasing oil?

Halderman: The American Petroleum Institute (API) has standardized tests and, if passed, can be shown on the container. This symbol is two circles, one inside the other. In the center is the SAE viscosity rating and between the inner and outer circle at the top is the API rating. The current rating is SM for gasoline-powered engines and CF-4 for diesel-powered vehicles.

API tests samples of the oil to make sure that it meets the specification. I recommend that you do not purchase oil that does not have the API circles. Several brands, including some synthetic oils, state that they "meet or exceed" the API standards, but without the API symbol, there is no verification of the quality of the oil.

Wheels: It looks like you need to look for two things when purchasing engine oil:

1. The correct viscosity (SAE rating)

2. The specified API rating (SM for gasoline engines and CF-4 for diesel engines)

Is this all?

Halderman: No. The International Lubricant Standardization and Approval Committee (ILSAC) standard was established to help make it easier for the customer to identify oil suitable for use in most gasoline-fueled vehicles. The current rating is GF-4 (gasoline-fueled) and includes a starburst on the front of the oil container. This starburst makes it easy to identify engine oil that is suitable for use in gasoline-powered vehicles. Therefore, for most, but not all vehicles, look for three things:

1. The specified viscosity

2. The specific API rating

3. The ILSAC starburst on the front of the container

Next week there are more specifications that must be checked. In the meantime, check the owner's manual for the specified oil to use in your vehicle.

James D. Halderman is the author of 12 automotive textbooks. Submit questions to him via e-mail at jhalderman2@juno.com, or write him at Wheels, Marketing Publications Department, Dayton Daily News, 1611 S. Main St., Dayton OH 45409.