Having a car fixed can be scary. The terms "flat rate," "service specials" and "time and material" are bandied about, with the occasional "I can't tell until we pull it apart."
You have choices. They may be similar to cable TV choices, like having 300 "B" movies available. You may not like any of them, but you do have choices. You can negotiate the method of charging for labor, and for parts, and for down time. You may not get what you want from the shop you want, but you can also choose another shop.
First, we need to explain the normal methods of charging. In the car repair industry, labor and parts are usually itemized separately. The labor part is calculated either by "flat rate", or "time and materials." Flat rate is the more common. That means the repair job is looked up in flat rate books to determine the labor times. These times are set by outside experts, not by your mechanic. They reflect the average time an average mechanic with average tools and equipment would take to perform a well-known repair procedure. Each shop has its' own labor rate, which is the amount charged per flat rate hour. If the rarer "time and materials" system is used, it means the repair time necessary is unknown, and you are being asked to pay by the hour as he works on the car. This is obviously a more risky deal, but sometimes necessary if, for instance, the procedure is not well known, or the problem is hidden and disassembly work is required to locate it. In these cases, flat rate books will not list the times. If a problem requires the time and materials method, the consumer would be wise to put a cap on it. For instance, if the shop wants to charge for diagnostic time, you can put a one or two hour maximum limit on it. If the shop hasn't found the problem by then, you probably need to choose another shop. You will, however owe for the time spent trying, if you agreed to do so.
Parts are usually sold at or near the MSRP, (manufacturers' suggested retail price), also known as "list" price. It is often possible for consumers to get the same discounts as the shops get from some vendors, and you might choose to buy your own parts. If, however, you take your own parts to a shop, you may get the same response you would get from a restaurateur if you showed up with a bag of groceries for them to prepare. A shop typically makes half its' money from parts and half from labor, so working without selling the parts brings in half the normal income, so they won't be thrilled by it, and may even refuse the job. In your interest, it complicates the warranty. Buying parts from the shop in most cases means the shop will replace a defective part in the future with no charge for labor. If they didn't sell the part, you will have to pay the labor charge to replace that defective part. This could be a substantial expense, costing more than you saved on the price of the part.
Conflicts arise. Consumers don't want to pay for repair time if a repair was not satisfactory. They say they should only pay for results, not effort. But if a two hour flat rate job is completed in one hour, they want to only pay for the one hour. They now want to pay for the effort, not the result. Many people demand to know what the repair cost will be before they bring the car to the shop. They feel the technician should know exactly what will be needed, sight unseen. He can't. If you demand an estimate before an inspection, you will not get an accurate estimate. Then there's the negotiation over down-time for the repairs. Technicians would like the owners to leave the cars and wait for a call when it's done. This can cause a melt-down in some people.
American life is so enmeshed with our cars, and we are so unwilling to use public transportation, that separating a citizen from their vehicle is like amputating a limb. If you demand a rush job, remember that the faster a person works, the more mistakes he makes. Fixing those mistakes results in more down time for the car and more time without pay for him. Nobody wins.
The best results come when the tech is given the opportunity to inspect the car first, before giving an estimate for both expense and down-time, and the consumer agrees. Once these numbers are agreed upon, all that's left is the easy part; the repair job, and the hard part; paying the bill. Like watching one of those 300 "B" movies, only better. You get something tangible from it; your car fixed.