Your BMW Spark Plug Wires act as the pathway between all the high-voltage electricity generated by your coil and your spark plugs. Since the voltages are so high, spark plug wires are recognizable from all the other underhood wiring you have by their extremely thick silicone jackets. This insulation keeps the spark inside the core, preventing it from jumping between wires and from grounding out on the engine block, causing a misfire.

The BMW spark plug wires in our cars aren’t as efficient as they could be, but that’s by design. Solid-core wires would transmit more electricity than the engineered-core wires that we use, but they also act like mini radio transmitters. If we used solid-core BMW spark plug wires, we’d have no radio reception, and the little radio waves would affect the operation of all the computer controls we count on for proper engine operation. So you lose a little efficiency with engineered-core spark plug wires, but the trade-off is worth it.