Being honest

My hubby dad has lived with us for a while. He’s a good man but has some issues. I love him but sometimes he makes me mad, or at the very least frustrated. One thing I have always valued in people is honesty, and directness. When someone is dishonest with me I have a hard time dealing with it especially if the dishonest makes no since at all. My father in law has a habit of lying if he thinks someone going to be angry with him. He doesn’t understand that okay maybe she won’t be happy with me if I tell her the truth, but she’ll know she can trust me. The other day dad just told me one to many untrue stories, and I pretty much gave him the I do not trust you.
The funny thing is the things he telling untruths about are things that don’t require it. Things I don’t really care one way or the other way it so simple I do not understand why not be honest. What did it for me I asked my husband if the doctor had said dad could drive. Dad has memory problems and sometimes he seems lost, and worried he won’t be able to find his way back. So we don’t want him driving unless he can tell us how to get home. We are happy to take him out, and bring him every where he needs to go and let me tell you, going out with dad is funner then buying women’s shoes.
Because dad always telling stories that aren’t exactly true, I am not sure at what point to trust him, or what part is simply just memory loss. I have pretty much decided to run things by my husband and if they both say the same thing then I know dad is probably remembering correctly.