Dayton Daily News

Halderman: This is the fourth of five columns devoted to engine oil.

Synthetic oil

Synthetic engine oils have been available for years for military, commercial, and general public use. The term synthetic means that it is a manufactured product and not refined from a naturally occurring substance, as engine oil (petroleum base) is refined from crude oil. Synthetic oil is processed from several different base stocks using several different methods. The categories of chemical compounds generally usable for synthetic engine oil include the following:

According to the American Petroleum Institute, engine oil is classified into groups as follows.

Group I - Mineral, non-synthetic, base oil with few if any additives.

This type of oil is suitable for light lubricating needs and rust protection and is not to be used in an engine.

Group II — Mineral oils with quality additive packages. Most of the conventional engine oils are Group II.

Group III — Hydrogenated
(hydroisomerized) synthetic compounds commonly referred to as hydrowaxes or hydrocracked oil. This is the lowest-cost of synthetic engine oils. Castrol Syntec is a Group III oil.

Group IV — Synthetic oils made from mineral oil and monomolecular oil called polyalpholefin or POA. Mobil 1 is an example of a Group IV synthetic oil.

Group V — Non-mineral sources such as alcohol from corn called diesters or polyolesters. Red Line synthetic oil is an example of a Group V oil.

Groups III, IV, and V are all considered to be synthetic because the molecular structure of the finished product does not occur naturally and is man-made through chemical processes. All synthetic engine oils perform better than Group II (mineral) oils especially when tested according to the Noack Volatility Test ASTM D-5800. This test procedure measures the ability of an oil to stay in grade after it has been heated to 300 degrees for one hour. The oil is then measured for percentage of weight loss. As the lighter components boil off, the oil’s viscosity will increase. If you start with an SAE 5W oil, it could test as an SAE 15W or even an SAE 20W at the end of the test. It is important that the oil you buy stay in grade for the proper lubrication of your engine.

Some types of synthetic oil are not compatible with other types. Some synthetic oils are mixed with petroleum base engine oils, but these must be labeled as a blend.

The major advantage of using synthetic engine oil is in its ability to remain fluid at very low temperatures. This characteristic of synthetic oil makes it popular in colder climates where cold-engine cranking is important. The major disadvantage is cost. The cost of synthetic engine oils can be four/five times the cost of petroleum-base engine oils.

During hard acceleration (or high-power demand activities such as trailer towing), the oil temperature will quickly increase. Oil temperature should not exceed 300 degrees.

James D. Halderman is an ASE-certified master technician, a member of the Society of Automotive Engineers and the author of 12 textbooks. Submit your automotive care questions to Halderman via e-mail at jhalderman2@juno.com, or write him in care of: Wheels, Marketing Publications Department, Dayton Daily News, 45 S. Ludlow St., Dayton OH 45402.