Final answer:
A dial indicator should be used to check for maximum piston clearance due to its precision in measuring small distances or changes in position.
Step-by-step explanation:
To check for maximum piston clearance, you should use a dial indicator.
A dial indicator is a precision measuring tool that can be used to measure small distances or changes in position without dismantling the assembly. In the context of piston clearance, it allows you to measure the gap between the piston and the cylinder bore.
In contrast, a feeler gauge might be used for less precise measurements such as valve clearances, a vernier caliper could be used for external measurements but may not offer the necessary precision for checking piston clearance, and a micrometer could be used for precise diameter measurements but is not typically used for gap or clearance measurements once the piston is installed.