Reviso ya sea el combustible o el kilometraje.

Reviso is the first-person singular present tense of revisar.

• revisar = the infinitive, to check / to inspect
• reviso = I check
• revisa = he/she checks or you (formal singular) check(s)

So if the subject is I, reviso is the correct form.

Ya sea ... o ... is a set expression used to present alternatives. In a sentence like this, it works like:

• either ... or ...
• sometimes whether ... or ..., depending on context

So ya sea el combustible o el kilometraje introduces two possible things being checked.

It is a little more formal or explicit than just using o by itself.

Yes. Sea is the subjunctive form of ser, but in ya sea ... o ..., it functions as part of a fixed expression.

A learner often expects it to agree with yo somehow, but it does not mean I am here. It is not directly tied to reviso. Instead, think of ya sea as one chunk meaning something like be it / whether it be / either.

So the sentence is not saying I am anything. It is simply using the expression ya sea ... o ... to list alternatives.

Yes. That would still be grammatical and natural in many contexts.

• Reviso el combustible o el kilometraje. = simpler, more neutral
• Reviso ya sea el combustible o el kilometraje. = a little more explicit, sometimes more formal, and it highlights the two alternatives more clearly

So ya sea is not always required, but it adds a nuance of either one or the other.

In Spanish, it is very common to repeat the article with each noun:

• el combustible o el kilometraje

This is more natural than leaving the second article out. While Spanish can sometimes omit repeated articles in certain structures, with two separate noun options like this, repeating el sounds clearer and more standard.

So a learner should generally copy the pattern:

• el X o el Y
• la X o la Y

Not exactly.

Combustible means fuel in a broad sense. It can refer to gasoline, diesel, or fuel in general.

By contrast:

• gasolina = gasoline / petrol specifically
• combustible = fuel more generally

So el combustible is a broader, more general word. In some contexts, English speakers might expect gas, but Spanish often uses a more specific or more formal term depending on the situation.

Kilometraje usually refers to mileage or the number of kilometers a vehicle has traveled.

Depending on context, it can mean:

• the vehicle’s accumulated distance
• the mileage reading
• sometimes the mileage rate or fuel efficiency in other contexts, though that is less likely here

In this sentence, the most natural interpretation is probably the mileage/odometer reading.

Because revisar is a direct transitive verb. It takes a direct object without a preposition.

So you say:

• Reviso el combustible.
• Reviso el kilometraje.

Not:

• Reviso de el combustible
• Reviso a el combustible

English learners sometimes expect an extra word like for, at, or on, but Spanish does not need one here.

Yes, revisar is a very natural choice for check / inspect / look over.

Other possible verbs depend on nuance:

• verificar = verify, check more formally
• comprobar = check, confirm
• checar = check, common in many parts of Latin America, more colloquial
• controlar = monitor/control, but not always the best match

So reviso is standard and widely understood. In everyday Latin American Spanish, you may also hear checo or chequear, depending on the region.

No. Kilometraje is widely understood across the Spanish-speaking world. It is not limited to Latin America.

That said, regional preferences can differ a little. For example, in some contexts people might talk about:

• el odómetro = the odometer itself
• las millas = miles, in places influenced by U.S. usage
• el recorrido = distance traveled, though that is not the same thing in every context

Still, kilometraje is a normal and standard word.

Not here.

Spanish normally uses o for or. It changes to u only before words that begin with an o sound, to avoid a clash in pronunciation.

For example:

• siete u ocho
• uno u otro

But here the next word is el kilometraje, which does not begin with an o sound, so o is correct.

The structure ya sea ... o ... usually presents alternatives, so it suggests one or the other, depending on the situation.

So the idea is closer to:

• I check either the fuel or the mileage

If you wanted to make it clear that both are checked, Spanish would usually use a different structure, such as:

• Reviso el combustible y el kilometraje.

So this sentence points to alternatives, not a combined list.