Learn Hardcore German: Wir gehen um acht Uhr los.

Wir gehen um acht Uhr. = We walk at eight o’clock (focus on the activity of walking).
Wir gehen um acht Uhr los. = We set off at eight o’clock (focus on the start of the movement).

Very often in everyday speech, when people talk about when they’ll leave or start an activity that involves going somewhere, they use losgehen rather than just gehen.

What is the infinitive of gehen … los, and why is the verb split?

The infinitive is losgehen. It’s a separable verb:

Infinitive: losgehen
Present tense (wir): wir gehen los

In main clauses, the conjugated part (gehen) goes into the second position, and the separable prefix (los) goes to the very end of the clause:

Wir gehen um acht Uhr los.
Morgen gehe ich früh los.

In forms like the infinitive or the future tense, the parts come back together:

Wir wollen um acht Uhr losgehen.
Wir werden um acht Uhr losgehen.

Why do we use um with the time? Why not am or something else?

For clock times, German normally uses um (+ accusative):

um acht Uhr = at eight o’clock
um halb sechs = at half past five
um 18 Uhr = at 6 p.m.

Some common prepositions with time are:

um
- time of day: um acht Uhr (at eight)
am
- day / date: am Montag, am 3. Mai (on Monday, on May 3rd)
im
- month / season: im Mai, im Winter (in May, in winter)

So um is the standard choice for a specific clock time.

Can I also say Wir gehen los um acht Uhr? Where should the time phrase go?

Yes, Wir gehen los um acht Uhr is grammatically correct and sounds natural.

In German, time expressions often appear near the beginning, but they are fairly flexible:

Wir gehen um acht Uhr los. (very common)
Um acht Uhr gehen wir los. (emphasis on at eight o’clock)
Wir gehen los um acht Uhr. (also fine, slightly more spoken-feeling)

The main rule is: the finite verb (gehen) must be in the second position in a main clause. All three versions respect that.

Is um acht Uhr one grammatical unit? What case is acht Uhr in?

um acht Uhr is a prepositional phrase:

um is a preposition that takes the accusative case.
acht Uhr is the object of um, so grammatically it’s in the accusative.

With bare numerals like acht and a time word like Uhr, you don’t see a visible case ending, but in grammar terms it’s accusative after um.

Why do we say acht Uhr and not something like acht Uhren?

When telling the time, German uses Uhr in the singular:

ein Uhr, zwei Uhr, drei Uhr, acht Uhr, zwanzig Uhr, etc.

Here Uhr is part of a fixed time expression, not counting physical clocks.

eine Uhr / zwei Uhren = one clock / two clocks (physical objects)
ein Uhr / zwei Uhr = one o’clock / two o’clock (time)

So: Wir gehen um acht Uhr los. = We set off at eight o’clock.

Could I leave out Uhr and just say Wir gehen um acht los?

Yes, in everyday speech people often drop Uhr when it’s clear that it’s about clock time:

Wir gehen um acht los.
Der Film beginnt um neun.

Both are perfectly normal. Adding Uhr is a bit more explicit and slightly more formal or careful, but both versions are correct.

Why is the pronoun Wir capitalized? Is that always the case?

Wir is capitalized here because it is the first word of the sentence. In German, the first word of every sentence is capitalized, regardless of its word type.

Inside a sentence, wir as a pronoun is written with a lowercase w:

Wir gehen um acht Uhr los. (start of sentence)
Um acht Uhr gehen wir los. (here wir is lowercase)

So: capital at the beginning of the sentence, lowercase elsewhere.

Does gehen mean “to go by foot” here? What if we’re driving?

Gehen usually means to go (on foot), to walk.

Wir gehen um acht Uhr los. often implies walking, or at least leaving on foot.

If you mean to go/travel by car, bus, train, etc., Germans often use fahren:

Wir fahren um acht Uhr los. = We set off / we leave (driving, taking a vehicle).

In some contexts, especially spoken German, gehen can be more abstract (“to work out,” “to be possible”), but for physical movement:

gehen → on foot
fahren → with a vehicle

Is the sentence talking about the present or the future? There is no werden.

Grammatically, it’s present tense. But in German, the present tense is very often used to talk about the near future, especially for planned events:

Wir gehen um acht Uhr los.
= We’re leaving at eight o’clock.
(like English present continuous for future)

You could also use the future tense:

Wir werden um acht Uhr losgehen.

This is fully correct, but in everyday conversation, speakers prefer the simple present for scheduled or agreed future actions.

Could I say Wir losgehen um acht Uhr or Wir um acht Uhr losgehen?

No, not as standalone main clauses. The conjugated verb must be in second position in a normal main clause:

✔ Wir gehen um acht Uhr los.
✘ Wir losgehen um acht Uhr.
✘ Wir um acht Uhr losgehen.

However, you can use losgehen together at the end of the clause in verb-final structures, such as after a modal, in a subordinate clause, or in the future tense:

Wir wollen um acht Uhr losgehen.
… weil wir um acht Uhr losgehen.
Wir werden um acht Uhr losgehen.

Is there any difference between Wir gehen um acht Uhr los and Um acht Uhr gehen wir los?

They mean the same thing: We set off at eight o’clock.

The difference is in emphasis and flow:

Wir gehen um acht Uhr los.
Neutral; a typical, unmarked word order.
Um acht Uhr gehen wir los.
Emphasizes the time (At eight o’clock is the important information). This might be used, for example, to correct someone or to stress the time:
- Nicht um sieben. Um acht Uhr gehen wir los.
  Not at seven. At eight we’re leaving.

Both are correct; choice depends on what you want to highlight.