So I recently carpooled on a trip with a friend. We were going to different nearby places around the same time, so we thought it'd be good to coordinate and drive together. City A, where I was staying was an hour farther from my home than City B, where she was staying. I'd planned to make 2 day trips to City B, which has a lot of museums, and drop her off, pick her up then.
At the last minute, after we got to our destination, she had to leave earlier in the day, so to get home in time, I had to cancel my day trip and just drive 2 hours, round trip to pick her up. Not ideal, but I'd rather it than my friend missing the very important thing she needed to do. Then, the gas money she gave didn't even cover the extra driving I had to to do to go to City B, let alone her share of the main trip.
I know some of this is my fault. I could've spoken up about the gas money at the time, and I think that ship has sailed. But I feel really taken advantage of, especially since I did a lot of extra driving with my 7 month old in the car, not an easy thing. But I've done this with friends in the same group, and have never had problems with the unspoken assumption that people will contribute fairly to the gas costs.
What could I do in the future to ask about gas money? Apart from not carpooling with this friend again, which I already plan to never do.