system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If you only had one gallon of gas left in your car, what would be the best way to get the furthest distance?

Say you are on the highway and notice you have only one gallon left in your tank and you don't know where the nearest station is. Assuming that time is not an issue and there are no other cars on the road and the road is perfectly flat, how could you get the most distance from that one gallon of gas? Would it be best to coast for a while, then accelerate back up to speed before coasting again and repeating, or would the extra energy of accelerating cancel out the benefit of coasting? Would just maintaining a constant speed be best? Or is there another method that would be better?
gpt
Your car will have an optimal speed for traveling the greatest distance per unit of gas, you would do your best to maintain as close to that speed as possible until you were out of gas.

The manufactures know this speed, through internal testing and math, but its pretty irrelevant to a consumer so there is no need to tell you it. It's likely between 40-60mph, again depending on the car and circumstances

Edit: One cool thing to add on.  Planes actually *know* the speed they need to do this type of activity, its a core part of flying (there are a few different ones with planes since you are dealing with more dimensions) and its used pretty regularly in flight planning.