Do I need anything else to use this wrench out of the box?

You'll need 3/8" drive sockets and extensions to fit your fasteners. The wrench itself is ready to go — just set your target torque and tighten until it clicks.

How do I maintain this wrench so it stays accurate?

Store it with the adjustment knob backed off to zero to relieve spring tension between jobs. Avoid dropping it or using it as a breaker bar — click-type wrenches lose calibration under shock load.

Is this wrench suitable for engine work?

This 5-25 N.m range handles fuel system bolts, intake manifolds, and light suspension work. For cylinder head or main bearing fasteners, you'll need a wrench with a higher torque range — check your engine manual for spec.