For as long as it’s been in the game, the DH Hornet Mk III has had 150 octane fuel while the DH Hornet Mk I has not. According to the pilot’s notes, both should have it! It sure would be nice if both versions were fully viable at 6.0! (Bug Link)
Also it really sucks that both DH Hornets have a fuel feeding bug that makes their fuel injection engines fuel starve under negative G. It’s been over a year and this really hurts them :( (Bug Link)