Yes, we really tried to do our best, it's nice to know that people notice it :)
In fact, I almost implemented the checkpoint auto-save system, but unfortunately it was right before the end of the competition, where bugs started to appear, which there was no time to fix, so we rejected this update.
So some parts of the gameplay involved intentionally restarting from the last checkpoint if the player didn't make it before the oil ran out, to better expose the oil mechanics, but time waits for no one :).
Thank you for playing our game and for your feedback, I appreciate it!