He quoted you for 4.. in their books they have have "how long it should take".. if his mechanic is good. he finished early. All auto mechanics do it this way. however.. what he said about 6 hours though.. I've never seen that happen.

The guy would quote me for 4 hours.. the book says 4 hours.. and if the job took 6 hours due to rusty bolts..etc..etc.. he would still only charge me for 4 hours..

I've been quoted for just a few hours.. and it taking all day.. and I still pay the price that I got quoted. It's not like he changed the number after he was done