Hours against age tells you how it lived
A machine averaging 400 to 800 hours a year has had a normal working life. Well under that usually means a machine that sat — seals dry out, hydraulics weep, and a low-hour machine that has been parked for three winters can be in worse condition than one that worked every week.
Far above it means a rental or production machine, run hard by operators who did not own it. Neither is disqualifying. Both change what you should pay.
Undercarriage is the number that matters on tracks
On a tracked machine, undercarriage can be 20% of the replacement cost of the whole unit. Ask for measured percentages on rails, rollers, idlers and sprockets, not a verbal 'good'. A dozer at 60% undercarriage and one at 15% are two different financial propositions regardless of the hour meter.
Hydraulics tell the truth slowly
Watch for drift: a boom that settles under its own weight, a bucket that creeps. Look for weeping cylinders, fresh paint around a cylinder rod, and oil that is milky or smells burnt. A hydraulic rebuild is five figures and it is rarely visible in photographs.
Ask what it was doing
The same 6,000 hours mean one thing on a machine that moved topsoil and another on one that broke concrete with a hammer all day. Application is the context the hour meter leaves out, and it is worth asking the house to get it from the seller.
From the auction floor
See how this works on a real lot.
Every listing carries its inspection report, its full specification and its bid history. Read one before you decide what it is worth to you.