These testers check the condition of antifreeze or coolant in an engine to determine if it needs to be flushed and refilled. Antifreeze and coolants regulate engine temperature when operating in extreme cold or hot environments.

Compression testers measure engine cylinder pressure to detect issues such as worn seals and valves.

These testers check diesel and gasoline quality to ensure the fuel has not oxidized or been contaminated with water.

These mechanical diagnostic tools are analog devices that test for issues in a vehicle's wiring to ensure electrical systems are functioning and receiving power.

These testers help ensure fuel injection systems are set up properly for correct injection timing and to avoid engine lagging from lack of fuel, or flooding from too much fuel.