Which makes sense. Most general aviation aircraft engines can run on petrol-pump fuel. Some pilots will land on dirt runways next to consumer gas stations. Petrol is cheaper than avgas. You can find videos of bush plane pilots getting a lot of confused on-lookers taking pictures of the airplane crossing the highway and pulling up to a gas pump. [1][2] Many of the experimental bush planes are using car and snow mobile engines Yamaha, Honda, etc... Car engines while not certified for aircraft are generally more fuel efficient, have longer time between rebuilds and operate better at higher altitudes, support higher RPM and have higher output power. The Zenith uses a Honda Accord car engine. [3]

Instead of a fancy flying car, I personally would just get something like Steve Henry's Highlander [4]. It has the Yamaha EPEX modified snowmobile engine and can take off and land in just a little more space than a helicopter. The wings can be removed by one person in 20 minutes.

[1] - https://youtu.be/PUSKBy3flAs?t=927

[2] - https://youtu.be/kSDJJn9lrkg?t=201

[3] - https://www.experimentalaircraft.info/homebuilt-aircraft/vik...

[4] - https://www.youtube.com/watch?v=zk4teJwQ6FI