Bottom Line
Maintenance Q & A
Clearing up classifications

By Paul Abelson, senior technical editor

Q. The guys at the shop where I get my oil changed say I need additive in my extended life coolant. They want me to buy a water filter with additive in it. I try to tell them that the old green antifreeze needed those, but the orange stuff only needs an extender at 400,000 miles or so.

Who is correct? Can you overtreat? I know Speedco checks the orange antifreeze with test strips, but I have never seen orange antifreeze need anything. Also, is all the orange stuff for trucks the same? If it meets some spec, it is interchangeable, right? Or is there a particular spec I should stay with?

A. Since you are using extended life coolants, do not use any supplemental coolant additives, whether in filters or separately. The "orange stuff" is based on organic acid technology, a chemical family that does all that SCAs do. The newest organic acid technology formulations prevent pitting, deter scale formation, and inhibit rust. Extended life coolants also contain water pump lubrication.

If ELC is diluted or contaminated with ordinary (green) coolant to about 10 to 15 percent, then it must be treated as if it were green coolant. That means you must use SCAs. You can overtreat. Too much SCA will gel and clog coolant passages, leading to overheating.

It is more advisable to drain the contaminated coolant and refill with organic acid technology-based extended life coolants. As you indicated, the extenders work well, adding several hundred thousand miles to coolant life. All extended life coolants are compatible and mixable.

Q. I have used one brand of oil since 1985. The guys at the shop have another brand supplied in bulk by a vendor. Is there really any difference between brands of oil?

A. Oils are formulated to pass multiple tests in order to get their grade designation. There are two sets of measurements for engine oil.

SAE viscosity measures the oil's flow characteristics both at cold temperatures and when the engine is hot. For example, a designation of SAE 15W-40 flows like an SAE 15 oil when cold, and an SAE 40 when hot. There is a trend in recent years to go to less viscous (thinner) oils, such as 10W-30 or, for extremely cold temperatures, synthetic 5W-40. Modern oil chemistry allows these thinner oils to perform well while improving fuel economy because they reduce internal drag through the oil system.

Service requirements:
The other consideration is the service designation. The American Petroleum Institute (API) and the American Society for Testing and Materials (ASTM) develop tests and minimum results for, among many other things, motor oils.

Each time there is a significant change in engines to meet tougher EPA emission standards, there is a change in the necessary properties of oils. A panel of engine builders and petroleum engineers determines what additional or upgraded tests are needed and what standards must be met.

These minimum standards are identified by two letter API service designations. Those starting with S are for gasoline, or spark-ignited engines, such as SJ, SL and SM. Those starting with C are for compression-ignition diesel engines. They also designate the stroke cycle, harking back to the days when Detroit Diesel made 2-stroke cycle engines. The latest are CI-4, CI-4+ and CJ-4.

The higher the second letter, the newer the set of requirements the oil must meet. The committee requires that oils be backward-compatible, meaning that a CJ-4 oil will perform in an older engine requiring CF-4, CG-4 or CH-4. Since these are minimums, oil blenders try to exceed them.

Oils differ by how much they exceed minimum requirements. All meet or exceed requirements or they are not allowed to display the API identification.

API samples oils on the market and tests to assure they meet standards. If not, they issue recall notices.

If you change oil according to manufacturer's recommendations, any oil that meets the API designation will work. If you extend oil drain intervals (always use oil analysis to determine and verify intervals), you may find differences in how far you can extend. LL

Senior Technical Editor Paul Abelson is a life member of OOIDA, holds an Illinois CDL, is active in the Technology & Maintenance Council and is a recipient of the Lifetime Achievement Award from the Truck Writers of North America. He can be reached at