Fueling a rental car

The biggest difference from the Gas Stations here in the US and in Germany is in Germany you pump then pay instead of the other way around. We have had no issue using our credit card in Germany. I can't give any advice about the discount cards, you may want to reach out to the individual company and ask them if their discount works over seas.

Make sure you know what kind of fuel your rental car uses. Diesal or gasoline.

In Germany we have also some pure self-service gas stations at huge shopping centres and at building / hardware stores.. There you can fuel like you know it from the US: paying /card charging allowance, choosing, fueling.

It is very unlikely that the discount cards will work because fully different legal entities in different countries.

You can save some money on fueling at the right time. In the morning hours gas is very expensive. There are some information portals to find the best time and cheap gas station in a region, e. g. https://www.clever-tanken.de/. Just enter the zip code or location name to get results.

Top 3 petrol station networks in Germany are Aral (belongs to BP), Shell and Total. Thus, you might check with BP and Shell if your discount cards are valid in Germany as well.
Prices are quite volatile and are indicated in Euros per liter.

Most important rule: Don’t use the petrol stations at autobahn rest stops, these are most expensive. Rather use those close to your accommodations or use the website/app mentioned by MarkK.

Everyone's feedback is very helpful! THANK YOU!

Recently, in Belgium, my cards did not work when trying to pay at the pump. The card worked perfectly well when I paid inside.

Thank you MarkK for that link. I have used an app >BenzinPreis< which is good but not great.

I was very glad to see that the diesel I bought yesterday is less than 2 cents € higher than the lowest in 20km. Thanks