Every local agency, as defined in Section 17518 of the Government Code, shall purchase lubricating oil and industrial oil from the seller whose oil product contains the greater percentage of recycled oil, if the availability, fitness, quality, and price of the recycled oil product is otherwise equal to, or better than, virgin oil products. This section shall not prohibit a local agency from purchasing virgin oil products for exclusive use in vehicles whose warranties expressly prohibit the use of products containing recycled oil.