Ojeté auto je levné.

Because they both agree with auto.

In Czech, adjectives must match the noun in gender, number, and case.
Here, auto is:

• neuter
• singular
• nominative (the subject of the sentence)

So the adjectives take the neuter singular nominative ending:

• ojetý → ojeté
• levný → levné

That is why you get:

• ojeté auto = used car
• auto je levné = the car is cheap

So both adjectives are shaped to fit auto.

A very common clue in Czech is the noun ending.

Many neuter nouns end in:

• -o
• -e
• -í

Since auto ends in -o, it is neuter.

That matters because neuter nouns require neuter adjective forms, which is why you see:

• ojeté auto
• levné auto

Other examples of neuter nouns:

• město = town/city
• moře = sea
• nádraží = station

Yes. Ojeté is a very normal word for a used vehicle, especially a used car.

The basic dictionary form is ojetý. In this sentence it becomes ojeté because it agrees with auto.

For cars, ojetý means something like:

• used
• second-hand
• already driven

So ojeté auto is the standard way to say a used car.

It comes from a verb related to traveling/driving, so historically it has the sense of something that has already been driven or worn by use.

In the present tense, Czech normally uses je here, just as English uses is.

• auto je levné = the car is cheap

You generally do not omit je in a normal sentence like this.

So:

• Auto je levné. = correct
• Auto levné. = not standard as a complete normal sentence

Czech can sometimes omit parts of sentences in headlines, notes, or very informal speech, but for ordinary grammar, keep je.

Czech has no articles like English a/an/the.

So auto can mean:

• a car
• the car

The exact meaning depends on context.

That means:

• Ojeté auto je levné. could mean
  A used car is cheap
  or
  The used car is cheap

In real life, context tells you which one is meant.

It is in the nominative case.

Why? Because auto is the subject of the sentence:

• Ojeté auto = the used car
• je levné = is cheap

The subject of a basic Czech sentence is usually in the nominative.

Because the noun is nominative singular neuter, the adjectives are also nominative singular neuter:

• ojeté
• levné

Yes, Czech word order is more flexible than English, but the basic version here is the most neutral:

• Ojeté auto je levné.

You may also hear:

• To auto je levné. = That car is cheap.
• Levné je ojeté auto. = It is a used car that is cheap / A used car is what is cheap.

But different word orders change the focus or emphasis, not the core meaning.

For learners, the safest neutral pattern is:

[adjective + noun] + je + [adjective]

So this sentence is an excellent standard model.

Auto is a very common everyday word for car.

It is shorter and more conversational than automobil, which is more formal or technical.

So:

• auto = car
• automobil = automobile

In everyday speech, people usually say auto.

A simple learner-friendly pronunciation guide is:

Ojeté auto je levné
≈ o-ye-teh OW-to yeh LEV-neh

A few useful points:

• j in Czech sounds like English y
• je sounds roughly like ye
• é is a long vowel
• stress is usually on the first syllable of each word

So:

• Ojeté → OY-eh-teh? Not quite. Better: o-ye-TEH in vowel quality, but Czech stress still starts on the first syllable.
• auto → AU-to
• je → ye
• levné → LEV-neh with a long final é

If you want a rough natural rhythm, think:

O-jeté AUTO je LEVNÉ

The dictionary forms are the masculine singular forms:

• ojetý = used
• levný = cheap

In Czech dictionaries, adjectives are normally listed in that masculine singular form.

But in your sentence they change to match auto:

• ojetý → ojeté
• levný → levné

So if you look them up, search for:

• ojetý
• levný

not just the forms from the sentence.

Yes. The adjectives would change to agree with the new noun.

For example:

• Ojetý vůz je levný.
  vůz = car/vehicle, masculine
  so the adjectives are ojetý, levný

• Ojetá motorka je levná.
  motorka = motorcycle, feminine
  so the adjectives are ojetá, levná

• Ojeté auto je levné.
  auto = neuter
  so the adjectives are ojeté, levné

This is one of the most important grammar patterns in Czech:
adjectives agree with the noun.

Usually it just means cheap/inexpensive.

So Ojeté auto je levné most naturally means:

• the used car is inexpensive
• a used car is cheap

Whether it sounds positive, neutral, or slightly negative depends on context, just like English cheap.

If you want to stress a more positive idea like good value or affordable, Czech might use other wording in some contexts, but levný/levné is the basic normal adjective for cheap.