Il sopralluogo cambia il preventivo.

Because sopralluogo starts with s, not with s + consonant.

Italian uses:

• il before most masculine singular nouns: il libro, il preventivo, il sopralluogo
• lo before masculine singular nouns starting with:
  • s + consonant: lo studente
  • z: lo zaino
  • ps: lo psicologo
  • gn: lo gnomo
  • x or y in many cases

Since sopralluogo begins with so-, where the s is followed by a vowel, the correct article is il.

Cambia is the third-person singular present indicative of the verb cambiare.

The subject is il sopralluogo, which is singular, so the verb must also be singular:

• io cambio = I change
• tu cambi = you change
• lui/lei cambia = he/she/it changes

So:

• Il sopralluogo cambia il preventivo
  = The site inspection changes the estimate

The verb form matches il sopralluogo, not il preventivo.

In this sentence, the word order is the normal Italian pattern:

subject + verb + direct object

So:

• Il sopralluogo = subject
• cambia = verb
• il preventivo = direct object

A native English speaker can often read this sentence in the same basic order as English.

So the sentence is understood as:

• The site inspection changes the estimate

not:

• The estimate changes the site inspection

If Italian wanted to emphasize a different structure, it would usually need different wording or context.

Because cambiare here is being used as a transitive verb, so it takes a direct object.

That means you say:

• cambiare qualcosa = to change something

So:

• cambia il preventivo = changes the estimate

You do not need a preposition like a or di here.

Compare:

• cambiare il programma = to change the schedule/program
• cambiare idea = to change one’s mind
• cambiare il preventivo = to change the estimate

It can do both.

1. Transitive: to change something

• Cambio il preventivo. = I change the estimate.

2. Intransitive: to change

• Il tempo cambia. = The weather changes.
• La situazione cambia. = The situation changes.

In your sentence, it is clearly transitive, because it has a direct object: il preventivo.

So here the meaning is to alter / revise / modify the estimate.

Italian uses articles more often than English, and in a sentence like this it is very natural to include them.

So:

• il sopralluogo
• il preventivo

both sound normal and complete.

The definite article can refer to something specific, or sometimes to something understood from the context. For example:

• Il sopralluogo cambia il preventivo
  can mean that the inspection (the one being discussed) changes the estimate (the one already mentioned or understood).

Italian generally prefers explicit articles where English may sometimes be more flexible.

Yes, but the nuance changes.

• Il sopralluogo cambia il preventivo
  sounds like a specific inspection, or a general statement about the inspection process in a known context.

• Un sopralluogo cambia il preventivo
  sounds more like a site inspection changes the estimate or a site visit can change the estimate, so it feels more general.

Both are grammatically correct. The choice between il and un depends on whether you mean something specific or more general.

No. This is a very useful false-friend warning.

In this context, preventivo means:

• estimate
• quote
• cost estimate

especially in business, repair, construction, or service contexts.

So:

• chiedere un preventivo = to ask for a quote/an estimate
• fare un preventivo = to prepare a quote/an estimate

It does not mean preventive here.

Yes, it is common in practical and professional contexts.

Sopralluogo usually means an inspection on site, site visit, or visit to the location before work is done or evaluated.

Typical contexts include:

• construction
• repairs
• real estate
• installations
• technical assessments
• event planning

So if a company says there will be a sopralluogo, it usually means someone will go to the place in person to inspect it, and that inspection may affect the final price or plan.

Yes. A few alternatives are possible, depending on what you want to emphasize.

For example:

• Il preventivo cambia dopo il sopralluogo.
  = The estimate changes after the site inspection.
  Here the estimate becomes the subject.

• Dopo il sopralluogo, il preventivo cambia.
  = After the site inspection, the estimate changes.
  This emphasizes the sequence of events.

• Il sopralluogo può cambiare il preventivo.
  = The site inspection can change the estimate.
  This sounds a bit more cautious or realistic in many contexts.

Your original sentence is direct and natural, especially if the speaker wants to stress that the inspection is what causes the change.

Yes, it is grammatically natural, but in real-life usage Italians might often choose a slightly fuller version depending on context.

For example:

• Il sopralluogo può cambiare il preventivo.
• Dopo il sopralluogo, il preventivo potrebbe cambiare.
• Il preventivo può variare in base al sopralluogo.

These versions may sound a little more typical in business communication because they are less absolute.

Still, Il sopralluogo cambia il preventivo is perfectly understandable and correct. It gives a clear cause-and-effect idea.