Is child support supposed to cover the cost of transporting child to and from a parent's house?

I am the custodial parent and receive child support from my daughter's father. Since our seperation over a year ago, I have been transporting my daughter to and from her father's house which is 60 miles round trip. He doesn't have a working car. I do this mainly so my daughter has time with her father. But, I also do this so that I can get some alone time. I am not working right now, so money is tight. I have asked for gas money once or twice and it is never freely offered to me. He thinks child support is supposed to cover the cost of gas and maintenance. This is ludicrous to me. What is WA State Law on this?