During vehicle refueling, which factor is controlled by maintaining metal contact between the nozzle and filler neck?

Maintaining metal contact between the nozzle and the filler neck during vehicle refueling is crucial for controlling static electricity. When fuel is pumped into the vehicle, it can generate static electricity due to the movement of fuel through the nozzle and into the tank. This buildup of static can create a spark, which poses a risk of fire or explosion if it ignites the fuel vapors present.

By ensuring that there is a continuous metal contact between the nozzle and the filler neck, the static charge is effectively dissipated back to the ground. This grounding mechanism reduces the likelihood of static electricity accumulation and helps ensure a safer refueling process.

The other factors mentioned, like temperature, flow rate, and vapor recovery, do not directly relate to the need for metal contact during refueling in the same way that static electricity does. While these factors are important in their own right, they do not address the primary safety concern of static electricity during the transfer of fuel.