Preventive maintenance schedule

For a fleet the schedule is a legal object. A motor carrier's record for each vehicle must include "a means to indicate the nature and due date of the various inspection and maintenance operations to be performed" (49 CFR § 396.3(b)(2)), beside the record of what was done and when. The federal carrier rule does not say how often to service anything; it says the record must show the nature and due date of what is to be done, so the schedule is a recordkeeping duty before it is a maintenance one.

Three things a schedule needs to be right per vehicle: the item's interval in its own measure, so an item keyed to engine hours is not computed from miles; the reading taken at this visit, so the next due is computed from a number someone entered on the order rather than an estimate; and the vehicle's own meters, which for a heavy truck means an odometer and an hour meter both.

In Wrenchy each maintenance interval is a seeded row by miles, hours or time, and each one shows as due or overdue against the reading on the order. The fleet page covers the account it belongs to.