For the rest of the non Americans this is 3.92L/100km for 594km, averaging 93kmh (58mph). 

Car is a 2025 Elantra with a 2.0L engine. Didnt use the AC and drafted with the slowest 18 wheeler I could find for the majority of the trip. It would've been above 60mpg if not for the 20 mins of stop and go traffic at each end of the trips. 

I do wish I had the hybrid version of this car to squeeze out even more miles, but I'm extremely happy with these results- my much older 2010 Corolla would be happy to see 40mpg under the same conditions so a 50% increase on efficiency is great. 

Also noticed a difference with wind resistance. Traveling against the wind I averaged about 57mpg, but on the return leg I was over 60 nearly the entire way. Even with drafting there is still a noticeable impact. Without drafting in these same conditions, I would normally average right over 50, maybe 52mpg.

Speed was a huge factor in this run being so efficient though. Highest I got at any point was 73mph, and that was to catch up to a trailer. Normally I draft behind faster 18 wheelers and see about 45-47mpg (which at those speeds id barely be above 40 without drafting). But driving slower gave an enormous boost to the overall mileage. Was nice to drive with no time constraints and find that sweet spot of efficiency! 

My best results so far