If your vehicle is showing oil pressure gauge drops to zero when stopped, here are the most likely causes and the parts you'll need to fix each one.
If your engine oil is significantly low, the oil pump may starve for fluid when the engine is idling, causing pressure to drop to zero.
The sensor that measures oil pressure often fails internally or gets clogged with sludge, causing it to falsely read zero at low engine speeds even when pressure is fine.
Oil that is too thin for your engine, or oil that has broken down due to age or fuel contamination, cannot maintain pressure at idle when the engine is hot.
As engines age, internal bearings wear down. The increased clearances allow oil to escape too quickly, dropping pressure when the oil pump spins slowly at idle.
The oil pump itself may be worn out internally and unable to generate sufficient flow at low RPMs to maintain system pressure.