Mia avino diras, ke salato kun oleo estas pli bona ol salato sen oleo.

Ke introduces a subordinate clause and usually corresponds to English that.

So:

Mia avino diras, ke...
= My grandmother says that...

In English, that is often omitted, but in Esperanto ke is normally kept.

In normal Esperanto writing, a comma is commonly placed before a subordinate clause introduced by ke.

So diras, ke... is standard punctuation.

You will often see the same thing with other clause-introducing words too.

The ending -as marks the present tense.

• diras = says / is saying
• estas = is / are / am

Esperanto verbs do not change according to the subject, so the same -as form works with mi, vi, ŝi, ili, and so on.

Esperanto makes comparisons with pli + adjective.

• bona = good
• pli bona = more good = better
• ol = than

So:

pli bona ol = better than

This is the normal Esperanto comparative pattern.

Because bona is not a direct object here. It is a predicate adjective after estas.

In the clause:

salato ... estas pli bona

the subject is salato, and bona describes that subject. Predicate adjectives stay in the basic adjective form unless they need plural or accusative agreement for other grammatical reasons.

So bona is correct, not bonan.

They are prepositions:

• kun = with
• sen = without

So:

• salato kun oleo = salad with oil
• salato sen oleo = salad without oil

After prepositions like these, the noun is normally just in its basic form, so oleo, not oleon.

Because the sentence is talking about salad and oil in a general way, not about one specific salad or one specific oil already known to the listener.

Esperanto uses la when the noun is definite or specifically identified.

So here:

• salato kun oleo = salad with oil, in general
• salato sen oleo = salad without oil, in general

If you meant a particular salad, then la might be needed.

Because Esperanto possessives behave like adjectives.

mia comes from mi and means my, but grammatically it works like an adjective, so it has the ending -a.

That also means it can agree with the noun:

• mia avino = my grandmother
• miaj avinoj = my grandmothers
• mian avinon = my grandmother, as a direct object

Here it is singular and not accusative, so mia is the correct form.

Avino is built from:

• av- = grandparent/grandfather root
• -in- = female suffix
• -o = noun ending

So avino means grandmother.

This is a very common Esperanto word-building pattern. For example:

• frato = brother

• fratino = sister

• patro = father
• patrino = mother

The repetition makes the comparison very clear.

The sentence compares:

• salato kun oleo with
• salato sen oleo

Repeating salato shows that these are two kinds of salad being compared.

Esperanto often repeats a noun when that makes the meaning cleaner and less ambiguous. Even if English might sometimes avoid the repetition, Esperanto is perfectly comfortable with it.

This sentence uses very normal, straightforward Esperanto word order.

Main clause:

Mia avino diras...

Subordinate clause:

ke salato kun oleo estas pli bona ol salato sen oleo

Inside that clause, the structure is:

• subject: salato kun oleo
• verb: estas
• complement: pli bona
• comparison: ol salato sen oleo

Esperanto word order is somewhat flexible, but this version is the most neutral and easiest for learners to follow.