I HAD TO MAKE a 335km trip today. I forgot to get gas last night. The car has a computer that indicates how far you can drive until the tank is empty. The computer said 277km. Not enough gas. I can only buy prepaid, tax-free gas at Esso stations, so traveling takes some planning. (Unlike American freeways with multiple gas stations every few miles, the Autobahn will only have one station every 50km (31mi) or so. (Yes, I can buy gas anywhere if I have to, but who wants to pay $8/gallon?)

The “distance to empty” calculation is based on the recent average fuel consumption. As I drive on the Autobahn, the average increases, and I am getting closer to the destination. About 75km into the trip, the “distance to empty” is 318km. This means I can make the trip w/o stopping for gas. But should I?

About the time I have all this calculated, I see an Esso station. Should I stop? Oh, I can’t stop. The exit is closed by a permanent construction site (“Dauerbaustelle” for those of you working on German vocab.)

No problem. Too early for gas. The math looks good. The kilometers-driven are increasing ever so slightly faster than the “distance to empty” is decreasing. Ninety minutes later, there is another Esso station. I still have a 50km cushion. The math looks good. Keep going. Uh oh. Big hill. Well, it turns out going down the far side recaptures most of the loss going up. Still have 50km extra.

At 125km “distance to empty” the little yellow warning light comes on. Hmmm. 125-50 is 75. How far is it actually until I get there? The iPhone shows I’m right at 75km to the destination. Good. The needle keeps falling. And falling. The computer is still reassuring me. Until…

The Autobahn is again hilly and full of curves. The needle is now almost touching the bottom of the markings. Hmmm. The math looks good. Can I trust the computer? Hmmm again.

I decide that I will stop at the next gas station. It’s better to be safe than sorry. I can always claim “I was pretty sure I’d make it, but just wanted to play it safe.” Sign says next gas station in 5km. Next sign says my exit is in 3km. No, it’s not the same exit.

I leave the Autobahn without buying gas. The needle is moving “below empty.” Hmmm. Maybe I should not have done this. It’s illegal to run out of gas in Germany. OK, next gas station it is. There isn’t a next gas station…

Every time the transmission shifts or there is a bump in the road I feel like the engine is about to quit from fuel starvation. Oh, why did I do this? The needle is so far below empty that I don’t know what’s going to happen. The computer says 44km of gas. The iPhone says 20km to the destination. What happened to my 50km cushion?

A crossroads ahead. GPS says go straight and the iPhone says turn right. Hmmm. The GPS is 20 years old. The iPhone is not. Turn right. Where the heck am I?

I get to the back gate of Tower Barracks (Grafenwöhr, Germany) and ask for directions to the gas station. When I get there, the computer shows 18km to empty. I put 56 liters in my 60-liter tank.

Average fuel economy: 31.3 miles per gallon or for Germans 7.9l/100km. I drove that tank of gas ever so carefully!