So, my old 2000 Ford Focus with manual transmission would be in overdrive at 75 MPH @ 2600 RPM

...on the other hand...

My 2018 McLaren 720S with 7-speed dual-clutch transmission would just be shifting into *2nd gear* at 75 MPH @ 8000 RPM (because I typically drive it at the outer edge of the traction envelope...since its all a dream anyway)

My McLaren is very inefficient when maintaining 75 MPH?

Yes, exactly. The Ford focus is more efficient at steady 75 MPH than the McLaren both because it's geared to turn less RPM (less explosions per minute), and because it's nearer to it's peak torque efficiency to maintain 75 MPH than the McLaren. IOW, the Ford requires more of the throttle to be open to maintain 75 MPH than the McLaren does. The Ford is generating the required power to maintain a given speed while using less gasoline compared to the McLaren.

This is a Brake Specific Fuel Consumption map for a Saturn 1.9L engine. It shows various engine speed and torque requirements to generate a given horsepower. The blue numbers on the right show horsepower, and any combination of engine RPM (bottom number) and Torque (left number) along this blue line will produce that same horsepower.

The closer you get to the red island in the middle, the more efficiently fuel is being converted into power. Lower numbers on the colored rings mean lower fuel consumption to produce a given horsepower for 1 hr.

Looking at the 20 HP blue curve on the right, you see that you can make that power at 4,500 RPM and a fuel consumption rate of 400 grams per kWh. Following that 20 HP blue curve, you can make the same power at about 1,750 RPM and a fuel consumption rate of 275 grams per kWh. Same power, less fuel consumption (and much higher torque). That 75% of peak torque line is very close to the sweet spot for efficiency. 80% might be ideal, but you don't lose much by going higher.

Notice you can't even get into the efficient red island without producing a minimum of about 30 HP, with 45 HP being right at about peak efficiency at 75% of the available torque and 2500 RPM.

Here's a graph showing typical power requirements to maintain a given speed. Notice that at 60 MPH, only 15 HP is required, which is nowhere near the 45 HP peak efficiency shown in the graph above. Peak engine efficiency wouldn't occur until about 90 MPH. Don't confuse peak engine efficiency with peak fuel economy though. As the graph shows, the power required to overcome drag increases with the square of speed. It takes 5 HP to drive 40 MPH, but 25 HP to do 80 MPH. That's 5x more power to go 2x the speed (rolling resistance goes up with speed too). What all this means is that the dinky 1.9L, 124 peak horsepower engine in the Saturn is still monstrously oversized to efficiently maintain 60 MPH on the freeway. It would be way more efficient to have a tiny 40 peak horsepower engine powering the car on the freeway, but then it would take an eternity to get up to speed, and the car would slow to a crawl going up hills.

Finally, here is a graph showing electric motor efficiency. At first glance it doesn't look so great, but then notice that efficiency only varies between about 85% and 95% throughout the RPM and torque range. It's pretty darn efficient no matter how hard or fast you run it.

Do you think the Infinity Q EV mission/application is to use such a large battery (if indeed its 20kW) as to pull 100's of kW on-demand at launch, yet transition into a very low current - almost overdrive effect - while simultaneously recharging the battery? IOW, the ICE is sufficient to propel the vehicle Only after its gained momentum from its battery. Is this efficiency enough to achieve 125 MPG?

Why does this sound as if their are some laws of physics being broken somewhere?

All of your assumptions sound correct to me, including doubting the 125 MPG efficiency. My guess is they are stating the

**MPGe** efficiency of the electric drivetrain, just as the Bolt is rated at 119 MPGe. There is no way the gasoline engine can get 125 MPG no matter how efficiently they convert mechanical energy into electrical. The first gen Honda Insight is about the most efficient hybrid car you can find, and it peaks around 70 MPG.

My guess is the car will get about 35 MPG, which is very respectable for a 400 HP, sub 4-second to 60 vehicle.