So let's sum things up: The LOI and similar documentary terms, are non standard, confusing, and lead to ambiguity. Documentary ambiguity is referred to in trade law as a condition "The Battle of the Forms" in which confusion from contradictory and ambiguous forms and documents damages the transaction. This should be avoided. To seasoned corporate traders and bankers, using terms like "Letter of Intent" is the mark of amateurs. What you properly want is an RFQ, request for quotation, from a seller or supplier. The seller may then reply to your RFQ with a quote OR full offer if they wish.
"Buyer who is serious, ready and able to purchase [crude oil], will sign [an] LOI and all the necessary documents that protect the rights of the Brokers and proceed. There is nothing to lose in signing those documents. This is how it is usually done and this is how it should be."