Learn Spanish (Latin America): Quizás el embrague sea más caro de lo que esperamos. - Perhaps the clutch is more expensive than we expect.

Adverbs of doubt like quizá(s) can take either the indicative or the subjunctive. Using the subjunctive (sea) shows a higher degree of doubt—the speaker is just guessing that the clutch might be more expensive. If they felt it was very likely to be more expensive, they could have used the indicative (es).

Is there a difference between using quizás and quizá in this sentence?

No, quizá and quizás mean the exact same thing and are completely interchangeable. However, speakers often prefer quizás before a word that starts with a vowel (like el) because the 's' makes the pronunciation flow a little smoother.

Why does the sentence use de lo que instead of just que for 'than'?

When comparing an adjective (caro) to a full clause containing a conjugated verb (esperamos), you must use de lo que (literally 'than that which') instead of just que. You only use a simple que when comparing to a noun or pronoun, like in es más caro que los frenos (it is more expensive than the brakes).

Prices change, so why do we use ser (sea) instead of estar for being expensive?