From an Entrepreur's perspective, time should be measured by calendar-months and be the primary optimization. Focus on efforts that will slash months from your company timeline.

Distraction is the real cost of a car breakdown: missing a meeting, finding a mechanic, bringing the car in, answering the mechanics phone calls, picking the car up according to the mechanic's hours, etc. Repair bill? Lost in the noise. If you're really optimizing, you live walking distance from the office to avoid distracting risks like this.

One reason to consider fixing the car yourself is to accomplish a fully engaging distraction as a break from work, the sort of thing that can lead to creative breakthroughs. If you can schedule it at the right time.