Lab Q&A: NOACK

Question: What is the NOACK Volatility Test and why is it important for engine oils?

Answer: The NOACK Volatility Test (ASTM D5800) determines evaporation tendencies of a lubricant (engine oil) in high temperature service.

The more an engine oil vaporizes (or evaporates), the heavier the oil becomes. Heavier, more viscous oil circulates poorly, which affects fuel economy, oil consumption and emissions. In addition, vapors travel where they are not supposed to go, like the air intake system.

Question: How is the NOACK Volatility Test measured?

Answer: The oil is held at 250˚C for one hour under a constant flow of air. This test simulates upper engine conditions.

The result measurement is the weight loss of the oil sample in mass percent (%).

Question: What are the NOACK limits for engine oils?

Answer: For API SN/ILSAC engine oils, the maximum evaporation loss limit is 15%. For API CJ-4 SAE 15W-40 engine oils, the limit is 13%. For API SAE 10W-30 CJ-4 engine oils, the limit is 15%.

Question: Where do most NOACK Volatility Test values fall for engine oils on the shelf?

Answer: BG performs many NOACK Volatility Tests each year on new engine oils in the market. Most conventional passenger car engine oils will be >13% while synthetic passenger car engine oils might be about 9–11%. Full synthetic heavy duty oil can be down to 8–9%.

Question: How do BG engine oils perform on a NOACK test?

Answer: NOACK values are listed on each individual product’s Specification & Technical Data sheet. For an example, BG SAE 5W-30 Synthetic Engine Oil, PN 737, has a value of 8.7% and BG Shear Power® HD, PN 716, has a value of 8.1%.

Question: Can oil additives reduce evaporation rate in an engine oil?

Answer: No. BG MOA® Engine Oil Supplement, PN 110, and BG DOC® Diesel Oil Conditioner, PN 112, can stabilize the oil in other ways. For example, antioxidants can improve oxidation control, but cannot prevent evaporation because this attribute has to do with base oil composition.