About 11 years ago, as I remember it, MoD(N) let a contract for oil in Trade Standard packaging. The Contractor supplied the said oil in plastic containers; and very stylish they were too. When the oil was stacked in the conventional manner in the stowage, the ones at the bottom deformed to such an extent that the stacks began to collapse. We went back to metal containers.
Sitting here in the relative comfort of a not overly warm office, I'm finding it hard to understand how it is difficult to read a label with O-160 and OX-26 or H-515 and OM-15 (as appropriate) marked in 1 inch high digits (as per DEFSTAN 05-52 Part 1). If the problem was the 1 litre tin, then that's very understandable as it isn't subject to the same labelling/marking standard.