When I bought my 2012 Volt just over 5 years ago, the salesman used "seasick mode" to describe driving in L. Perhaps this is what your wife objects to... the transition from moving to slowing down is more jerky than smooth. It’s fine for the driver, who’s expecting it, but not so comfortable for a passenger. Best use I’ve found for L is to keep the car at a steady speed using Cruise Control when heading downhill. The following is my understanding of how the Gen 1 Volt handles regen (Gen 2 has two planetary gears and may differ in operation). I would appreciate feedback if I have it wrong...
I think of the Volt as a 1-speed when "going," and D and L are for "slowing down as you coast," or "D"ecent coasting vs "L"ousy coasting. The Gen 1 Volt’s primary traction motor is a marvelous thing. When electricity flows through the coils, the motor’s shaft turns, and via the connection to the drivetrain, the turning of the motor’s shaft applies torque to the wheels, making the car move down the road. When the foot comes off the accelerator, the wheels continue to roll, and if they’re still connected to the motor via the drivetrain, they can apply torque to turn motor’s shaft, transforming it into a generator. Can’t do both at the same time.
Of course, shift into Neutral, the connection is broken, the wheels continue to go round, and the car coasts down the road because of the momentum of the car.
With the foot off the accelerator, the car’s momentum is harnessed to turn the generator shaft, which consumes the car’s kinetic energy and slows it down. By adjusting the generator’s circuits to increase or decrease the output (the regen), one controls the amount of torque required to turn the shaft, using up the car’s kinetic energy slower or faster. In D, the "slowing" effect of the regen is minimal (but still, more than if you shifted into Neutral). In L, you get more regen, and you slow down faster. The Volt’s motor/generator is not connected to the brake lights, so using regen to slow the car won’t light up the brake lights, and that can be dangerous if the car behind you doesn’t know you’re using electricity, not friction, to slow your car rapidly.
The Volt uses blended braking (starts with regen, ends with friction), so the brake pedal, one could say, gives the driver the ability to manually adjust the "slowing down" setting until you reach the point where the friction brakes are applied. The brake pedal is the only "regen level" device that is also connected to the brake lights.
Next, of course, comes the part where the Gen 1's gas engine gets clutched to the smaller motor/generator, and generates electricity to fuel the primary motor to give your Gen 1 Volt "electric-like" performance when the battery is depleted or you switch into Hold mode...
I don't spare the electrons or the gas.
