The oil additive needed to start the trolley is located in a locked store room inside the sales office. To unlock it, pick up the flashy remote on a desk to turn on a TV. You will see a commercial about some product from Umbrella Corp. Make note of what the product is. Here are some that you might come accross: Safsprin, Adravil, Aquacure. Go to the nearby computer where Carlos just shot his zombied friend. You will be prompted for a password. Type in the name of the product. The store room is now unlocked.