Does flying a small GA aircraft use less fuel than driving the same distance by car?

Question

This is a notable claim by Friedrich Merz, head of the CDU party and a member of the German parliament:

„Ich bereue nicht, dass ich zur Hochzeit von Christian Lindner geflogen bin. Um es mal auf den Punkt zu bringen: Mit meinem Kleinflugzeug verbrauche ich weniger Sprit als jeder #Dienstwagen eines Mitglieds der #Bundesregierung. Und deswegen fliege ich.“

(Link to Tweet)

Translation (via deepl.com):

"I have no regrets about flying to Christian Lindner's wedding. To put it in a nutshell: With my small plane I use less fuel than any #servicecar of a member of the #federalgovernment. And that's why I fly."

I'm very skeptical about this claim with regard to fuel usage. Aviation fuels cannot easily compared to fuel used for cars. Thus, it is hard to say what "uses more fuel" actually means. A literal reading would probably compare those fuels by volume in litres. Whilst I'd appreciate debunking or verifying the claim on that basis, I'd also be interested in how the carbon footprint stacks up (car vs plane) to be able to judge if — even if the literal claim would be true — it might be misleading.

Another thing to consider: How many electric cars are available for members of parliament. If an electric car had been available, this would debunk the literal claim immediately, but again, a comparison based on the carbon footprint (what kind of energy mix was available that day to [re-]charge the car) would be interesting.

Also relevant for discussion: The route via plane might be shorter than via car (although not necessarily). Answers should focus an the general claim (car vs. plane) but also consider the special circumstances of this route. I have not been able to find the actual flight data recording of the route.

The aircraft in question seems to be an DA62 (Source, in German).

Answer 1

This article (in German) has done further research and calculations that all seem to add up. Their verdict is that Friedrich Merz's flight did not use less fuel than other German cabinet member. In fact, the only member that could potentially have caused more or an equal amount is chancellor Olaf Scholz, because his official limousine is heavily armored and therefore very heavy. Merz's literal statement can therefore be considered false.

I will translate the key paragraphs here:

Radarbox tracked Merz' flight with an estimated flight duration of 2 hours. The producer of the aircraft estimates 44.7 litres of fuel per flight hour at 60% capacity. Other sources estimate more based on test reviews, around 56 litres per hour. This means the flight might have used up to 112 litres of diesel - roughly equivalent to Scholz' limousine with 109 litres. Calculations from the Swiss Federal Agency for Civil Aviation estimate the CO2 equivalent of Merz's flight at 282 kilograms, whereas Scholz's drive would have caused 35 kg less.

Other members of German parliament do not even drive such heavy vehicles or even use electric cars, whose equivalent CO2 output is way less. Cem Özdemirs drive with an Audi e-Tron Sportback 55 would have caused 46 kg of real CO2 emissions.