What does it mean if I added oil?

Does this mean putting gas in my car?

This is a joke on the Internet: the boss's female assistant asked the boss to borrow his Maybach: "Boss, where is your car? Lend it to me?" The boss said: "It's in the backyard. Is there any gas?" If it's too much, remember to add gas to me when you get back." The female assistant returned the car key to the boss, and the boss said, "Did I add gas?" The female assistant mumbled, "No, I didn't even start it. If you don’t, you know you’re going to blackmail me.”

When the female assistant borrowed the boss’s car, the boss reminded her to refuel the car when she came back. But when the female assistant returned the car, the boss asked her if she had refueled. The female assistant said she had not because she knew the boss might blackmail her. This joke implies that some people may take advantage of the kindness of others to achieve their own ends, and it also reflects some people's suspicion and distrust of the kindness of others.