Glad to have helped!
On the topic of the speedometer, that is tricky. I wonder, if you are willing to experiment a bit, how the game will feel if you shift the mechanics around a bit. I have three ideas regarding this issue.
One, make the fuel give the player a boost (like a boost pad or nitrous). This one would rely heavily on spawning algorithms and map design so the player isn't thrown headfirst into a wall constantly.
Two, make slowing down drain fuel faster rather than instant death. It'd change things drastically and make slowing down an option for players at the cost of more fuel. So if they needed to go slower for a bit, but felt they could reach the next fuel, they might try to use this option.
Three, make slowing down kill player after a delay. There would be a countdown on screen and could even be less than a second. The advantage is that this allows for slower drifting (more movement) as well as the scenario you mentioned notifying the player when it happens. On the flip side, the player could take advantage of this method pretty easily. You could also implement it as a kind of shield. In this case, the "countdown timer" would start at a value (say 2 seconds) and would never refill until player death. so they could use a bit of the time to break before shooting off in a different direction, but they could only do this so many times.
Of course, feel free to discard these ideas, it's your game after all! Hopefully if they aren't useful by themselves, they at least help you a bit in coming up with a solution. Good luck on turning this into a full game!