Why the change from the old way?

The online method is simpler to run for the oil manager and offers more features for users.  The old method was a group email (and some phoning for the no replies to check email address was correct), then collating all the replies to give a total order, then phoning suppliers for quotes.  All that takes time.  By using a web site then users are responsible for keeping their email up to date and entering/changing their order.  The site does the group email, totals the order, emails the suppliers.  The oil manager's job is just to trigger the buy, then to collate the replies from the suppliers to find the cheapest, to place the order and update the supplier details on the buy. The site emails the users all the details.  As you can see this saves a lot of drudge work.