From my experience, the money charged by a mechanic has nothing to do with how reliable and professional they are. When most of the #car parts are now available at great prices from different competing parts manufacturers, the hourly labour rates are rising sharply and are not justified by the amount of certificates the mechanic has earned over the years, but are purely dictated by personal ambition.
The amount of time one spends asking around for quotes is paid off within just a few visits to different #mechanics, especially when it is understood (or you let them know) that you are asking for more quotes and will eventually go with the best offer. Your 'loyalty discount' for always trusting the same mechanic is automatically given to a new customer who understands this procedure and takes the time to #shop around.
Reading the owner's manual allows you to understand the maintenance required and when it should be done. No one understands the car better than the #manufacturer and knowing when you should change the oil, the different filters and the spark plugs will ultimately save you money when the mechanic wants to change parts based on a generic spreadsheet when you know that these parts should still be in good working condition for the next x-amount of years. Learn about the type of oil the mechanic is using and which oil your car requires - with this simple #knowledge you will know how many miles and months the oil is good for, and if there are better alternatives to the one you are currently using.
Understand that the mechanic may be known to be very thorough but you are the one paying for his perfectionism in labour costs and changing of parts that don't need to be replaced...
Knowledge is power and money! Making a bit of an effort to understand your car issues is easy. Just google your cars make and model and you will find a dedicated forum with owners willing to help others from their own personal experience. Almost every issue you have with your car will have an online explanation of what it is and what you should do. Whenever a warning pops up on the dashboard read about it in the owner's manual, read more about it online and other owners' experience, and only then contact your mechanic and their competitors.