Delo 600 ADF, a new heavy-duty engine oil produced by Chevron, contains just 0.4 percent sulfated ash, which reduces the rate of diesel particulate filter clogging and can improve fuel economy retention by as much as 3 percent, the company claims. The oil meets API CK-4 specifications and has demonstrated good oxidation stability in industry, OEM and field tests, as well as extended drain intervals. The oil delivers good valvetrain wear protection and piston deposit performance and hit the market in December in SAE 15W-40 and SAE 10W-30 viscosity grades. Web: www.chevronlubricants.com