When I leveled to level 100 my maximum fuel increased from 116 to 124, but after doing a Bigboy run on normal, which should use 10 fuel, it put me to 111 fuel rather than 114. This has continued since leveling to 101.
Also, in the past when I spent tokens to refill my fuel when I have some fuel remaining it would add that remaining fuel to my maximum fuel and wouldn’t be wasted. Since leveling to 100, if my fuel goes over 124 that fuel is wasted because after doing Bigboy on normal my fuel is always 111 afterwards, regardless of how much over 124 it was beforehand. This has happened both after refueling when I had 2 fuel remaining, putting me to 126/124 fuel and when I got the daily login reward of 15 fuel, putting me at 139/124. Both times I did normal Bigboy once I had 111 fuel afterwards.