The long Lisle 18232 Offset Funnel, and its smaller cousin, the Lisle 17232 Right Angle Funnel, work well with big trucks, RVs or vehicles where the oil fill is obscured or located in a tricky place.

He considers the simple case, shown in Fig. 1, of a right-angled “funnel” in two dimensions only, truncated so that the diameter at the end BC is twice that at AD. Taking a point O on BC he ...