Paul Turnbull of Munro & Associates uses the GM Equinox EV’s drive unit teardown to explain why GM chose a mechanical oil pump over an electric one, and what the true engineering trade-offs are.
Key insights:
Electric oil pumps offer precise flow control, delivering more cooling at low speeds and less at highway speeds, which improves range and protects the motor under extreme conditions.
Mechanical oil pumps are cheaper because a gear replaces the motor windings, magnets, and control electronics, and GM leveraged its existing high-volume automatic transmission pump production to cut costs.
However, the fixed gear ratio forces the mechanical pump to over-deliver oil at highway speeds, requiring GM to add a plastic deflector to prevent spin losses and oil foaming, adding cost and complexity that offsets some savings.
The decision made clear financial sense in 2019 when electric oil pumps were costly low-volume parts, but as EV production has scaled into the tens of millions, electric oil pump prices have fallen dramatically
The Munro’s core message is that engineering decisions must be evaluated on fully accounted current costs rather than historical bill-of-materials figures.