Question

a penny can be used in which part of vehicle maintenance?
checking oil level
checking tire tread depth
monitoring emissions
checking brake fluid

Explanation:

To check tire tread depth, insert a penny into the tread with Lincoln's head facing down. If you can see the top of Lincoln's head, the tread is too worn. This is a simple, common - sense method. Checking oil level uses a dipstick, monitoring emissions requires specialized equipment, and checking brake fluid uses a dipstick or visual inspection of the reservoir (in some cases).

Answer:

checking tire tread depth