Ol Shy & Bashful wrote:

For the club time as you are looking at, figure as soon as you start
the engine you're on the clock for cost and that is the most common
method.

Ol Shy:

Thanks for the response. Are you recommending that I simply plan for
the Tach amount for the flight time? There is a $12 per hour
difference between the Tach and Hobbs rental price (Hobbs is
cheaper). Sounds like a bad deal to me if there is no way to optimize
engine performance to at least 90% of the tach reference RPM.