A couple of months ago I bought a 02 mustang gt with 4.6 v8 with around 76,7XX miles. When I bought it I was told that recently they did an oil change. It has a sticker for 75,300 miles that was changed. It now has 77,300 miles on it. I decided to change it and it was black. I looked at the oil filter and the original owner wrote the date, 1/3/2019. I changed the oil and filter and now I need to change the air filter. Does anybody think that the moter was damaged, and if it is what can I put in or do to at least minimize the damage? I mostly put in highway mileage if it matters. No problems so far but just to be sure
You'll be fine. Motor oil turns black in every engine it goes into, even brand new ones. The oil has detergents in it that dissolve crud and carbon, and hold it in suspension in the oil so it'll be removed with an oil change. The black coloration is the crud in solution. It sounds like it sat for a long time with the same oil in it. If you're really paranoid, you can check your oil level every few weeks, depending on how much you drive, and monitor the level. There probably won't be any issue.
If it had a sticker I assume the last oil change was done at a shop of some sort like jiffy lube? They may not have changed the filter for whatever reason. May be they didn't have one that fit, who knows. I don't think the engine was damaged based on the mileages you provided. I would not use any type of additive, just the manufacturer recommended 5W-20 conventional or synthetic blend oil.
If the oil that came out wasn't chunky, or had glitter in it, then I wouldn't worry about. Same with the filter. Used oil SHOULD be black. That means that it's doing its job.
What you don't want to see in oil is:
1. Any chunkiness
2. Anything that glitters
3. Anything that looks like a milkshake
4. A large amount of water (some condensation is ok)
I would change the oil and filter and move on. The 4.6L V8's are tough motors and I doubt anything was damaged, especially if you don't have anything shiny/glittering in the oil.
