All I know is that if you plan on a gallon to jamb everything, you will end up short 1 quart. Murphy's Law you know, always figure for more. Every car is different, and different colors (and coverage) is also a factor. If you are getting good results, then just bite the bullet and buy more paint, I'm afraid it is just the way it usually goes. Just my , no need to quote the crap out of me today!