Motul SAE 30 is a monograde engine oil, meaning it has a single viscosity rating with no multigrade viscosity improvers in the blend. That is exactly what many pre-war and early post-war engines were designed around, and it is also what some stationary and small engine applications still specify. Running a monograde in an engine of that era is often the more sympathetic choice, since the very large clearances and low oil pressures of early designs were engineered on the assumption of a straight grade. The 2 litre bottle lets you make up an unusual sump capacity accurately rather than guessing. Use it where a straight 30 is genuinely specified, not as a general substitute in a modern engine calling for a multigrade.