does it do any damage to the car if.....?

NO it won,t hurt it , Just be careful about doing it to much, When I had a straight shift I did it all the time and no problem Its not good to always do that to an automatic, hope this helps

Your breaks will wear out faster in the long run. Plus, if you switch back to2nd gear or whatever and the car is going fast you could damage the gear box. Why would you that ?to save gas? Not a good idea. You won't really save much anyway.

no but the damage happens when you try to put the gear back in at the wrong speed

On a car with manual gearbox--No. But with an automatic gearbox it could damage the gearbox due to lack of lubrication.

The short answer is no.

However if you have power assisted steering and/or braking then then have the engine running.

if its has a manual trans then NO. if its an automatic trans, for towing purposes only,and no faster than 30mph yes.

You are a hazard to all other road users and risking your life....friend!

No, it will actually save on gas.

it will hurt automatics badly

I hope not cause I do it loads!!