The Shulchan Aruch (536:1) addresses the case of a person who needs his horse for a trip on Chol Ha'mo'ed, and to this end he must have the horse prepared for travel; for example, he needs the horse to be saddled and the iron shoes affixed to its feet. The Shulchan Aruch rules that if the individual needs to travel on Chol Ha'mo'ed and cannot reach his destination by foot, then he may have his horse prepared for the trip during Chol Ha'mo'ed.
Chacham Bentzion Abba Shaul (Jerusalem, 1924-1998), in his work Or Le'tziyon (vol. 3, 24:5), applies the Shulchan Aruch's ruling to the issue of bringing one's car to a mechanic for servicing on Chol Ha'mo'ed. If a person must travel on Chol Ha'mo'ed, and he cannot reach the destination by foot and does not own a second car, then he may bring his car to the mechanic to have it prepared for driving. One may not, however, bring his car to the mechanic on Chol Ha'mo'ed to have it prepared for a trip he will make after the holiday, or if he has some other means of reaching the desired destination on Chol Ha'mo'ed.
Sometimes people bring their car for servicing specifically during a week when they anticipate not needing to drive it; this would be forbidden on Chol Ha'mo'ed. One may bring his car for servicing on Chol Ha'mo'ed only to prepare it for trips that he must make during Chol Ha'mo'ed.
