Wow, I got this one gold very easy first try.
But then I'm an economical driver in real life & always have been. ha ha
I remember reading "tips for saving fuel while driving" and realizing I was already doing all of them.
I would like more challenging contests of this nature!
I think mostly it's about not rushing up to corners. (In real life, not rushing up to red lights.

)
I was rather leisurely in getting up to speed, and then not so worried about getting back up to speed after getting through corners.
It's more about just maintaining momentum than anything else.
Don't go so fast that you can't get through the corners nicely without having to jam the throttle to get out of the corners.
Knowing the nice lines on the track of course helps.
And I think racing the track in very low power cars often has also been good practice for getting good lines & keeping momentum at speed.
In a low power car you don't have the power. In this challenge, you don't have the power because you don't have the fuel.