AVISTAR / INTERNATIONAL DIESEL engines with Hydraulic Electronic Unit Injectors, used in Ford pickups, vans and school buses, sometimes suffer drivability problems due to oil foaming. Leaching of RTV silicone from the oil pan gasket into the oil causes the foaming. Foamy oil interferes with fuel injection, which reduces engine power.

The ASTM D 892 Foam Test, Sequences 2 and 4, are used to evaluate diesel oils on their foaming characteristics relevant to this engine. Recent testing performed by an independent lab shows the results below.

According to test results, AMSOIL Synthetic 15W-40 Heavy Duty Diesel and Marine Oil (AME) and AMSOIL Series 2000 Synthetic 5W-30 Heavy Duty Diesel Oil (HDD) are clearly not prone to foaming or contributory to the foam-caused drivability problems of the IH engine.

The test also shows AME and HDD dissipate foam more quickly than Rotella T, a popular diesel oil often recommended by Ford. Faster foam dissipation means reduced foam related drivability problems.

You should know that silicone leaching diminishes with increased engine mileage, and in the meantime the solution to foam-induced drivability problems, regardless of oil brand in use, is an oil change.