It enables higher compression so you can get more power per unit of engine weight, but the fuel efficiency per gallon is lower.
And the lead is for the valves.
You can get more efficient planes but you can’t overcome the need to fight gravity at some point.
Some aircraft and definitely not drons for now.
So they should have much better efficiency than typical quadcopters
But the term commonly refers to all unmanned aerial vehicles.
For example a Global Hawk unmanned aircraft can fly 14,000 nautical miles and remain aloft for 42 hours. They are by definition very efficient. That is a drone.
On the other end of the spectrum The Spirit of Butts' Farm crossed the atlantic with 118 US fluid ounces (3.5 L) of fuel. It was flying for ~39 hour and 1,881.6 mi (3,028.1 km). That is about 2045 mile per gallon if I count it right. That is very efficient, and of course since the aircraft was unmanned it is a drone.
Wow - this is what they are planning to use to deliver packages?
> In fact, unless you drive a car that gets 33.8 gallons per mile (or carry more than one passenger), new airplanes coming off the assembly line are more fuel-efficient
Cars typically get about 0.03 gallons per mile, so it’s not even close.
There's also the simple practical issue: self-driving cars can't navigate a complex crowded environment, whereas self-flying planes navigate a much simpler environment with many more regulatory controls on behavior.
[1] https://www.sustainablebusiness.com/2014/02/surprisingly-air...
[2] https://www.flyouts.com/vliegtuig/cessna-172