Traders are better off NOT using documents like LOI, ICPO, FCO, etc. Even if and when they rarely are used in internal trades, on a restricted level within specific industries, they have no legal or customary basis in International Trade whatsoever. In fact the presence of many of these terms are considered to be signs of Advance Fee Fraud, by knowledgeable players and law enforcement.
HOW VALID, OR OTHERWISE, ARE THESE USUAL RATIONALE BY SELLERS OR THEIR AGENTS? Ironically, while oil sellers and their agents frequently demand that prospective "serious" buyers involved in crude oil transactions should first offer an LOI, the buyers, on the other hand, are not generally enamored of that idea.