I don't think you will find sarcasm in my original post.
I was however trying to gently make the point that HVLP is much more environmentally friendly than the old style spray guns. Is also makes less mess and overspray in your painting area. It also uses less paint and therefore less thinners or reducers. It also paints as well or better as the older guns, subject to opinion of course, but I have never heard anyone knowledgable say HVLP paints any worse than an old style spray gun. Also answered, was that yes, it will run off your old compressor.

I would not paint a car with a 3hp compressor. However, a 15 gallon tank with a 3hp motor will paint any giant scale model just fine. I can paint a car with my 26 gallon/5 hp compressor. I usually run low on air 75% through the job and must pause for 60 seconds while the tank fills enough to finish. That is a lot of paint being applied.