How do I calmly ask my friend for gas money for work rides without hurting his feelings?

I actually never ask strangers for advice, but I need help figuring out how to talk to my good (M) friend.

We've been close friends for 16 years. His car is broken right now, and he asked me to drive him to work for four days (only Thursday and Friday). I'm a soft person and I'm willing to help him, but I don't want to pay for all the gas myself. Right now, I'm running out of ideas on how to say this without hurting his feelings.

Here is the situation...

1. Uh, I don't drive much. I usually walk to work (only about 5 minutes), so I only fill my gas tank every two weeks. My friend...these rides will use up the gas I was trying to save.

2. His girlfriend has a bad history of damaging his cars. From what I've seen and been told, she has broken several of his previous cars. His current car is also broken because of something involving her while she was doing DashDoor. She apparently drives very long hours (12–16 hours) without taking proper breaks.

3. She's totally jobless, has used his name on loans, and takes his money, so he is often short on cash, plus pay money for her two lovers in the prisons. They always broke when his paycheck is coming.

4. He recently asked me that he wants the rides until he can buy the parts to fix his car, but I don't know how long that will take before my boyfriend and I move out of Austin, Texas for Dallas, TX next month.

I don't want to start an argument or make this all about his girlfriend. I just want him to help cover the gas for these rides. I can't cover the full cost or the extra mileage.

My questions:

1. What is a calm and clear way to ask him for gas money?
2. How can I say it so he understands I still willing to help, but I need him to pay for the gas?
3. Any advice on how to word the message, or how to handle it if he tries to negotiate or gets defensive?

So, I'm all ears for your advice.