more carbon-efficient than a bus because it has eco

You can just hear the salesperson saying this.

The fact that you keep capitalizing Me makes it sound like you are God, and your friend took You to church, lol

If you are alone on the bus, it’s worse, but I dunno how many you need to offset it. You also should travel a bit farer because of rider pooling. But ridership quantity should offset this usually

eco is a button that prioritized fuel efficiency over performance with the engine. It does not do a whole lot but I keep it on. I might consider turning it off if I was towing something but would likely do a search and see if it was necessary or not.

And he said his petrol car is more carbon-efficient than a bus because it “has eco”. I still don’t know what eco is,

Eco is probably a particle filter. It doesn't mean it doesn't pollute, or even pollute less... Just that certain particles are now captured.

Eco is a button that doesn't let you accelerate as fast, so that the combustion efficiency is higher (probably closer to 20% efficient instead of 5% efficient when accelerating fast)