Large number of questions

[Hakurei]

What does realistic fuel consumption setting do in either state? I have it on, on the assumption that it will work essentially by RPM. If that's right, what is it based on when turned off? Speed?

What is the difference between the two 12-speed transmissions? I've seen it mentioned that the higher level one is an overdrive (lower revs/fuel consumption while cruising) but I can't tell the difference for myself.

Sometimes when I start my truck after resting I find the air tanks are empty. What causes this?

Why do truck cabs rock when braking and accelerating?

Can anyone tell me the masses of the trailers in the High Power Cargo Pack?

And what cargoes are added by Vive la France? Like Scandinavia added livestock.

Is there a mod that adds exhaust smoke?