I work flatrate now.
It can be a double edged sword!
If you are good, have most of the special tools and are willing to work 50+ a week the $$$$ can be very good. However if the shop or the mechanic is slow it gets hard to pay the bills and can be VERY seasonal.
For the customer it can get high or it can protect them from crooked people riding the clock so to speak. By using the book you cant overcharge as the mechanic will only get that much no matter how long he takes to complete the job.
Brad
