Recently, I sprayed the inside of the doors and underside of the hood of my 1986 F150 project truck. It's shadow blue metallic, ford paint code 7B. Back in 2013, I took it to a guy who was going to paint it for me, but he wound not being able to finish the project. I had forgotten that he had purchased paint for the project, and after 13 years, I had forgotten about it, too. It's been in a climate controlled environment since the truck came home, back in 2014. Recently, in preparation for paint the truck myself, I purchased 2 gallons of paint and reducer (same brand as before) and sprayed the underside of the hood and inside of the doors. I know it's just paint, but I was overthinking, and wondered if the older paint was still any good if I ran short, so I put it on the paint shaker for a while and then popped the clips off and opened the first can. There was no sludge in the bottom, so this morning, I sprayed a test panel with the same black sealer as the doors and hood, and then a couple coats of clear. Soooo.... My question for the group, should I mix the 2 older gallons with the 2 newer gallons, or just a couple quarts of older paint with the new paint to make sure I have plenty in case of having to respray something? Would the color change between the inside of the doors and the rest of the truck be noticeable enough to require those to be scuffed and resprayed? I am going to have to fix a screwup on one door anyway, so respraying it wouldn't be any more trouble. What do you guys think? Opinions, advice, suggestions welcome.