Gas vs Oil Shocks

Yes, in most cases it does. A gas shock that stays compressed has lost its charge through a worn rod seal, and the oil will now aerate under hard use, even if the shock still feels firm by hand. Keep in mind that the test says nothing about damping force, so a shock that does extend is not necessarily healthy. An oil shock never extends on its own, so the test does not apply to it. It is also worth looking for oil on the body, and replacing shocks in axle pairs so that both sides damp alike.

Yes, for light-duty use where cost and a soft low-speed ride matter more than resistance to fade. That usually means older vehicles that came with them from the factory, or cars that rarely see rough roads or heavy loads. On a vehicle that tows, carries heavy loads or uses unmade roads, a gas shock is the safer choice, since an oil shock will fade there long before it wears out.

The strap holds the rod in against the gas charge, so that the shock stays compact in the box and is easier to fit between the mounts. The usual method is to fit one end first, keep the strap on while you line up the other end, and then cut the strap and guide the rod out to the mount. A rod left to spring out freely can strike your hand or damage the seal. If the shock has rubber eye bushings, tighten the mounting bolts to the specified torque with the vehicle at its normal ride height, because tightening them with the wheels hanging preloads the bushings and shortens their life.