Spark ignition ICEs experience something called “pumping losses”: There’s a physical impediment (the throttle) that the engine has to work against at low engin

Spark ignition ICEs experience something called “pumping losses”: There’s a physical impediment (the throttle) that the engine has to work against at low engine speeds. So while drag increases with speed, it’s also true that at lower speeds you’re still converting hydrocarbons to waste heat at the same rate. The truth is that fuel economy is a delicate balance between rolling resistance, aerodynamic drag, gearing, and the engine power curve.