Where do you live G88?
If its hot year round where you live 10W40 or 20W50. If not 10W30. Everyone has their own brand. I grew up on Valvoline. Puralator Pure One or Mobil One filters are some of the best.

 

I would recommend 10W30 or 10W40. I wouldn't use synthetics unless you're sure the engine has been rebuilt since '81 or '82. The gasket materials used prior to those years are different materials and synthetics will eventually leak past the seals/gaskets. Whatever you use, use a quality name-brand oil and filter(I'd recommend Motorcraft-but that's just an opinion).

 

Thanks for your help. How much oil do I put in?

 

Is there anywhere I can get a manual for this car that tells you how much oil to put in and stuff like that?

 

5 qts. Fills my 289 up. I use 10w-40w or 20w-50w. Need to keep the oil pressure up. I flush mine every 6,000 miles or so. I started it went I rebuild it. If you have never done it on you motor and you got 70,000 miles on it, don't flush it. It could be bad news.

 

Start with 4.5 Qts. Start the engine(with the new filter installed), when there is oil pressure, shut the enngine down. Check the level, add as necessary. I've found that 289's fill up on just under 5 Qts.

Any Mustang parts vendor should have a factory manual for the car. Haynes and Chilton books are good, but not as good as the factory manual, as they usually cover a wide range of years. The manuals run about 35 bucks, Chilton or Haynes about 15. The latter books can be found at any auto parts store.