Grammar issue

Thanks.
Is them incorrect or unnatural in my sentence?
You have written two sentences. Are either correct?

Also possible: The mechanic has advised them to take...

khoshtipIs them incorrect or unnatural in my sentence?

Yes.
I recommend a solution to someone.

"to" is needed with recommend because recommend is not a ditransitive verb.
Here is a list of these verbs. Probably there are others

AlpheccaStarskhoshtipYou have written two sentences. Are either correct?Yes.

I'm a little puzzled. The way I'm reading this thread, you seem to be implying that the following sentence is correct:

Their mechanic has recommended to take their car to a foreign car expert.

Is that what you mean?

I got it! Thank you.

It's common to say
eg Their mechanic has recommended taking their car to a foreign car expert.

AlpheccaStars"to" is needed with recommend because recommend is not a ditransitive verb.

Look at this sentence from M.M, please:

would you recommend me to your boss;
It is here:

Here, recommend acts as it is ditransitive, apparently.

khoshtipwould you recommend me to your boss; [...] Here, recommend acts as it is ditransitive, apparently.

It looks more to me like a monotransitive verb and a prepositional phrase.

These are examples of using verb recommend:

Their mechanic has recommended to take their car to a foreign car expert.
Their mechanic has recommended that they take their car to a foreign car expert.
Their mechanic has recommended taking their car to a foreign car expert.

And sometimes that verb acts as it is ditransitive