I phoned regular oil company to get a price for my oil - girl quoted £469 - I made a bit of a mistake saying that "oh I can get it for £433 - oh yes came the reply I can match that. Then I remembered another cheaper quote of £419 and she consulted her supervisor and said "oh I can match that too". I have ordered but another unsuspecting person would never know to ask.
Over the last 27 years we have had oil found this negotiation works well in a falling market but not so well when the oil price is rising. They know then if you decline their offer they can get more for it in a few days.