Critical Reasoning Sprint - 19 (GRE)

The new Altis Delight, Altis Auto’s flagship electric-gas hybrid automobile, is considered so efficient by Altis that the company plans to sell the Delight to consumers for no payment other than the difference between what the consumer paid for gasoline for the past three years of driving their previous vehicle and what they will pay for gasoline while driving the Delight for the next three years. Consumers will make an initial down payment, and then pay any remaining fees after fuel costs have been assessed at the end of the three year period.

Which of the following, if true, would most significantly disadvantage Altis Auto based on their proposed payment system?