It's not only the additives. Oil majors like Shell, BP, Exxon et al do have a tendency to insist on more stringent shipping standards, whereas those that supply supermarkets may cut corners, not so much in terms of ship quality, that is all pretty much of a muchness nowadays, 15/20 years ago, not so much. More in terms of ship cargo history, which although may lead to cheaper transportation costs, can (not necessarily will) lead to product contamination.
Generally though it's much like anything else. Cheap doesn't always equate with quality. Not so important when you're bunging it in a tractor or a 20 year old car, but the modern ones with sophisticated computer controlled engine management systems tend to be more sensitive. |