Map of highway fuel stops in Germany

When I was stationed over there in the early 2000's, you could buy a map from Esso that had all their other stations located on the map. If you're looking for a non-tech solution to make sure you can get fuel, this is one option.

When I traveled to Germany a few years ago (US citizen) I realized that my cell phone plan wouldn't have data service over there, and as such, Google maps would be useless. I looked around for a GPS app that allowed you to pre-load maps, and eventually decided on CoPilot GPS (I have no association with the app, just a satisfied user.)

You do need to pay for maps, but you get the first one for free, to let you see if you even like the app. I chose the pack with Germany (which includes Austria, Switzerland, and Liechtenstein, which is nice.) I found the maps to be as accurate as could be expected, and were very helpful for getting around in a country I'd never been to before (and where my language was rather rusty!)

If you have a smart phone with GPS, I cannot suggest it enough. It should certainly help you find your way, without having to worry about roaming charges or foreign data plans. Even if you don't take it with you, maybe their maps will be updated enough to help you plan in advance.