Word for the money that is paid for a carpool – equivalent word to the German informal word "Spritgeld"

In German there's the word Spritgeld which is a compound of petrol/fuel and money. So, the verbatim translation is petrolmoney or fuelmoney, respectively.

This is an informal word which is commonly used when talking about the money that one owes someone else for a drive that they took together. Example sentence:

Wieviel Spritgeld schulde ich dir?
≈ How much money do I owe you for the drive?

I'm looking for a translation for Spritgeld. I couldn't find anything on the Internet. I found some words like

• gas/fuel/petrol allowance/reimbursement
• mileage reimbursement/allowance
• travel expenses reimbursement

but I feel that all those terms are of a pretty formal register. I consider them to be the counterparts to the German (more or less) formal terms Fahrtkostenerstattung and Kilometergeld/-pauschale.

Is there an informal term that you would use when you ask or tell someone how much money your/their share for the drive is?

It's almost a direct translation: "gas money." Here's an example of the usage from the novel WWW.MATE by Tamaya:

She wanted to pay me for [the gifts], but I declined. After all, she was a friend, always driving me around when I needed a lift somewhere without taking or asking for gas money.

In British English, "petrol money" would be universally understood and used by native speakers for exactly this situation.

An example would be the title of this thread.

I agree that "gas money" would be how English-speakers would identify the concept. However, in my experience, it wouldn't be referenced directly in your context. I think American English-speakers would generally phrase it something like "How much do I owe you for gas?" It's quite a bit less-awkward than phrasing it, "How much gas money do I owe you?"

They might go on later to refer to the incident like, "I gave John twenty bucks gas money"; but even then, "I gave John twenty bucks for gas" would be more likely.