RANT! In lawsπŸ˜’πŸ˜’πŸ˜’

I am so fed up.
My mil (mother in law) borrows my car to work since she works kinda far and her truck wastes to much gas. Well I let her take it but I told her I also need a car for my kids appointments so she said to take her truck. It's been 3 times that my husbands dad takes the keys to work & I don't understand why since he has his car. So I told her that I needed the truck since I had an appointment that day but somehow she doesn't like to tell him anything since he's a moody old man && he knows I need it as well as he knows that she takes my car so why is he constantly taking the keys?
Does he not trust me with their truck or what? I seriously don't know what to do and I feel bad for constantly telling her how much I need the truck & she just doesn't tell him anything.
I'm just at a point where I feel like telling her not to take my car.
I feel horrible about it but my kids appointments are pretty far and I can't walk with them especially all 3 of them. 
What should I do? Please help