How does gas usage in a car work? What makes me use more or less gas?

Question

So I know driving takes gas, and having my lights on costs battery power. But somehow driving charges the battery? Does that cost me extra gas? And what actually costs me gas also? Does standing still with the motor on cost me gas? If I have heating on max? If I have airco on max? What kind of driving costs more or less gas? I am so confused with this all. I dont feel like I am doing anything insane in my car, but still the total amount of km I can drive varies so much on a full gas tank. It goes from 600 to 400 and I have no idea why. I hope there is someone who can explain this to me

In: Engineering

Answer 1

> Does standing still with the motor on cost me gas?

Yes, and this is the biggest factor. Whenever the motor is running, it’s continuously burning gas, that’s what is making it run: exploding the gas.

The variation is mostly caused by how much time you’re idling (standing still) vs driving. City driving uses more gas per km because you have to factor in all the time stopped at lights, driving slower in roundabouts etc. Highway driving uses less gas per km because you’re moving forward the whole time your engine is on and burning gas.

Also maybe in the winter you remote-start your car before going out to drive? The whole time it’s running in the driveway, the engine is burning gas and you’re going zero distance.

Other factors:

-Gas engines get the most power out of the gas in a pretty narrow range of engine spin speeds (rpm). So aggressive acceleration uses more gas to get to the same speed than speeding up gradually, because accelerating hard pushes the rpms above the most efficient level.

– The faster you go the more air resistance there is. There’s a certain speed with a balance between the best rpms for the engine efficiency meets the increasing air resistance of going any faster. The number depends on the vehicle. Driving faster than that uses more gas per distance than going slower.

– I’ll let others cover this better but yes heating/airco do (indirectly) use gas by draining the battery. Mythbusters did a study on this.