[sokoloff]

It matters if OP is multiplying the hours they spent times $100 rather than the time the mechanic would quote (usually from a flat rate manual) times $100/hr.

If a pro mechanic would charge me $100/hr times the book time of 1.3 hours to change pads on my car and I take 3 hours to do it, I saved $130, not $300.

For simple jobs, I can usually match or slightly beat the book rate. Because I don’t have a lift, a lot of undercar work takes me loads longer.