Divorce, kid and car

I really don't like fighting with my ex-wife.

We rarely do fight.  Friends tell me I have one of the most civilized divorces in the history of divorce.

We share custody 50/50, never bad mouth each other to the kids, and handle decision making with cool business-like detachment.

But when we do come up at odds, and if I express it, a lot of under the surface resentment bubbles up.

My son is 16.  He's a good kid, never gets in trouble, studies hard---an honor student. I told him that I would give him my 2009 Nissan Altima when he got to this age.  I bought myself a truck and handed him the keys on his 16th birthday.

My dad bought me a $500 beater the day I turned 16.  I could have done the same for Jonah, but I wanted him to have reliable transportation.   And I wanted to reward him for working so hard at his studies.

I didn't discuss this decision with his mom, as she doesn't discuss similar decisions with me.  We generally do what we think is best for our kid without consulting each other.

Fast-forward six months.  I'm making payments on Jonah's car and I asked if his mom would cover his insurance payment.   I explained why I thought this fair.

It's now a tense situation.  She's called for a group meeting between myself, her new husband, my wife and me.  I'm not sure we need a sit down with our significant others to discuss our children.

I told her I'd call her.  I tried. No answer.