Etiquette Dilemmas

I agree with PP. Ask her once or twice, but if she doesn't help, then the most you can do is not travel with her anymore. In the future, I would start the trip with a full tank, and then fill up right before you drop her off. This way, she's only paying half of the gas that was used on the trip, and can't say anything.

I hate when people assume that you're going to cover gas because it's your car. When I travel with my mom, I don't always cover gas IF she's going with or without me (since she'd be using it anyway), but at the very least, I will definitely buy her lunch on the road and pay for the tolls. When we take my car, it's the same idea - I cover the gas, she covers food/ tolls.

In situations like this, I usually start with a full tank and then fill up from there, when they're with me so we have a receipt to just split.

Other than long trips though (more than an hour or two one-way) I usually cover gas if I'm the one driving. My friends and I will just switch it up. One friend has a child so when she comes she drives and then I'll just cover her lunch.

I'd ask once or twice and then leave it at that.

Melissa

This happened to me before years ago.
Because in those days I was less assertive,
I said nothing and really resented my friend
for it.

In this case you had a clear agreement to split
the cost of gas and you discussed it three times
with her. There is nothing greedy about holding
her accountable to her side of the agreement.

You said she has taken advantage of you before
so you should assert yourself in this case, or
she will continue to do things like this in the
future. And you need your money! $40 is a lot.