Is it permissible for the owner of a petroleum transportation company, who is contracted with an Italian company that does not fulfill its financial obligations, to take the extra liters he receives from the refinery to settle his debts, knowing that the Italian company is aware of this surplus and may have reduced the price based on it?

As long as the company is aware of the increase and has authorized the customer to be charged for it, the increase is rightfully the customer's and does not belong to the truck owner or its driver. The truck owner is not permitted to take the increase, even if the company procrastinates or does not pay him a satisfactory fare, because the increase belongs to the customer. The truck owner can pursue his right through legal channels, and if the rental amount does not satisfy him, he may choose not to renew the contract upon its expiry.