What does Level indicate on Flying Mounts?

Darksylph - Heavens Tear

Ok simple question that i cant find an answer to. All flying mounts have a level (hover over the mount and you'll see it in the popup). The initial mount at 30 is level 1, and in the boutique, 3 of the flyers are level 2, and one is level 4. This is not an indicater of their speed, as the level 2 mounts in the boutique are all different (+1.0, +1.5 & +2.0) and the Level 4 mount is +1.5. I used to think this indicated how many more times it could be upgraded, but after looking at the aeroforge, i see that all flyers can be upgraded to +3.0 speed regardless of their level. So, can anyone tell me what that flying mount level indicates? I ask cause i finally have the money for a better one and want to incude all facters in my decision on which to get. ATM i'm looking a Rashnu (+1.5) because i dont like the oversize look of Nakir's, but if the fact that it's level 4 means something that could effect my decision i'd like to know.

Devoted - Lost City

The level grade corresponds to what type of fuel crystal you need to add fuel. Decomposing gears gives you those crystals and 3 level 1 = 1 level 2 etc.

Darksylph - Heavens Tear

At last an answer XD. Ok so level 4 would be technically worse as its more expensive. But i have yet to ever refuel so its not a big issue. Thanks for the response ^^.