What are the legal consequences for a tourist who runs out of gas on the Autobahn?

As Klettseb already wrote in his answer, you can actually get fined for running out of fuel in Germany, but his explanation of the legal basis and the list of expected fines are incorrect.

To avoid different interpretations of the colloquial terms 'halten' (stop) and 'parken' (park), the German traffic law uses narrow and precise definitions:

Halten ist eine gewollte Fahrtunterbrechung, die nicht durch die Verkehrslage oder eine Anordnung veranlaßt ist. VwV-StVO § 12 (1)

Wer sein Fahrzeug verlässt oder länger als drei Minuten hält, der parkt. StVO § 12 (2)

Translated to English:

Stopping is an intentional interruption of the ride not caused by traffic circumstances or command.

Whoever leaves his vehicle or stops for more than 3 minutes is parking.

As you can see, both terms are intentional actions. If your vehicle stops moving due to some unintentional circumstance, you are by the definition of the German traffic law neither 'stopping' nor 'parking'.

Running out of fuel is instead fined as a violation of StVO § 23. A vehicle operator is expected to make sure that the vehicle he is operating is in a suitable technical condition for the intended ride and running out of gas is considered a violation of this requirement. The regular fine is €25 (TBNR 123112), but it can be increased to €80 (TBNR 123600) if you substantially impair traffic safety or to €120 (TBNR 123601) if you cause an accident.

The questions from the OP are:

1. What happens if a tourist runs out of gas on the autobahn and not aware of German autobahn law, how to cope with this situation?

2. Drivers finding themselves in this predicament can be subject to fines?

3. Penalty is same for everyone regardless of nationality?

The key point in question is, naturally, the Latin phrase ignorantia legis non excusat — not knowing about a law does not excuse and does not prevent punishment (in German, the phrase is often cited ‘Unwissenheit schützt vor Strafe nicht’, which explicitly includes the punishment). This is also relevant to contraventions and most ‘illegal’ things relevant to drivers and driving are contraventions. § 11 of the Ordnungswidrigkeitsgesetz (OWiG, contravention law) reads:

§ 11 Irrtum

1. Wer bei Begehung einer Handlung einen Umstand nicht kennt, der zum gesetzlichen Tatbestand gehört, handelt nicht vorsätzlich. Die Möglichkeit der Ahndung wegen fahrlässigen Handelns bleibt unberührt.
2. Fehlt dem Täter bei Begehung der Handlung die Einsicht, etwas Unerlaubtes zu tun, namentlich weil er das Bestehen oder die Anwendbarkeit einer Rechtsvorschrift nicht kennt, so handelt er nicht vorwerfbar, wenn er diesen Irrtum nicht vermeiden konnte.

Loosely, this translates to:

1. Who at the time of infraction is not aware of a circumstance that belongs to the offense is not acting with intent. The possibility of penalties due to neglecting behaviour remains.

2. If at the time of infraction the offender does not realise they are doing something illegal because they did not know about the existence or applicability of a regulation, they cannot be penalised if they couldn’t avoid the error.

So which paragraphs actually apply? For one, there is § 18(8) of the Straßenverkehrsordnung (StVO, traffic code), which disallows stopping on motorways. This includes parking. There is also § 18(9) which forbids pedestrians entering the motorway. For these, the Bußgeldkatalog (penalty catalog) defines the fines of €30 (stopping), €70 (parking) and €10 (entering as a pedestrian). Since these values are defined in annex 1, (fahrlässig begangene Ordnungswidrigkeiten — carelessly committed contraventions) § 11(1) of the OWiG does not apply.

§ 11(2) applies if you could not under reasonable circumstances have found out about the existence of such a law. However, that doesn’t apply at all. Since there was no exceptional haste involved in renting a car/travelling to Germany, you could have, under reasonable circumstances, found out about the rule that disallows you stopping on a motorway and leaving your car. You are expectet to read up on travel regulations before you enter a country. This is akin to being required to know that in Germany a red traffic light means ‘stop’ and not ‘stop, but if you want to make a right turn proceed cautiously’. So § 11(2) won’t help you, as many internet sources including this one state. In theory, the fine applies.

In practice, the police often have better things to do than to check up on a car that is standing on the sideline. They have all reason to assume just a regular breakdown. Since you cannot evade a breakdown if it happens, you cannot be liable to pay a fine in that case. Thus, chances are high that you will get away with it. Unless of course the police see you refilling from your jerrycan — if they catch you doing that it is very likely that you are wrongdoing. Be prepared for questioning and a good excuse.

The best (and safest) strategy if you ran into the situation is to call a service car to tow you to the next petrol station (or off the motorway; whichever is quicker — note that an additional fine applies for not leaving the motorway at the earliest possible moment when towing). If one is just in sight, you can attempt to get away with walking over there, buying a 5 litre jerrycan and filling your car with that.

Naturally though, the prime strategy is not to run into the situation at all. Every petrol station on the motorway will be accompanied by a sign noting the distance to the next one, giving you enough time to decide whether you want to risk it. And of course, it is least hassle to just not run into the situation altogether.

The above text should have answered the first and second question. For the third, different fines for different nationalities would be a violation of the European anti-discrimination act if European nationalities are involved — this is the key point why the currently discussed road toll cannot be implemented in its current form. Regardless of European legislation, any differentiation according to nationality (except where something only applies to foreign nationals per se) would be considered discriminatory and likely not make it past the constitutional court. So yes, in theory all fines applicable are the same for everybody regardless of nationality.

The previous replied pointed out that motorists must take proper care of their vehicle to avoid hazards, which includes watching the fuel gauge.

That being said, the police are allowed to prioritize how they deal with minor infractions if there are too many to handle, and all German police forces have problems with accumulated overtime. So they may decide to ignore the infraction. Or they may not.

The basic assumption of the question seems to be that German (or any other) law distinguishes between tourists and other subjects.

I am not aware of any country with such a distinction.

Of course, the actual enforcement of a given law might differ for a tourist, but this does not happen at the level of the law.

The penalty is the same for everybody, regardless of their nationality.

But in practice the decision on whether to enforce the penalty is up to the police officer at the scene. For a minor infraction like this, it really depends on their mood as much as anything else. Some police officers would tend to be more lenient towards foreigners; some might tend to be less lenient. As always, the best approach is to be polite and apologetic.

Anyway, what excuse could you give? "I wouldn't have run out of fuel if I'd known it was illegal"? That is not at all convincing!

I'd like to address the possibility to run out of gas on the German Autobahn, since nobody seems to include this in their answers and most comments were deleted.

The chances of you running out of gas on german roads is very small. Just pay attention while driving and get gas early. Every gas station along the highways has a sign that says how long it will take before you will meet another gas station. This was you can determine wether or not you need to stop right now, or later on on the trip.

So in my opinion a good second question is; 'How likely is it I will run out of gas on the German Autobahn?' and my answer to that is: Very unlikely, if you pay attention and don't wait until the very last moment to refuel.