I recommend Amsoil. They have a written warranty for anything their oil is used on. If your engine fails because of the oil, they will replace it. No one's made a claim in 34 years. Decent track record there.

 

I run Rotella in my 65 because, in my estimation, it is the best dino oil on the market. However, my 65 has high mileage on it and running synthetic in it would make it leak like a sieve. I run Royal Purple synthetic in my 03 Mach1. Amsoil, Redline, Royal Purple and Mobil 1 are all good synthetic oils. There are a bunch more on the market, and Mobil 1 is the cheapest and most readily available. You can buy it a Wal-Mart, whereas, you will need to contact an independent contractor (dealer) to buy Amsoil and Redline. I can get Royal Purple at the little parts store here in my little town, but it is around 9 bux a quart, and my Mach holds 7 quarts. Amsoil and Royal Purple both claim you can run the car 5K miles, change the filter, then run the car another 5K miles before changing the oil.

 

Amsoil is 25k/1yr on oil and filter. Always been 25k on the oil, but redesigned their filters to last as long as the oil instead of half as long.

 

when switching to synthetic i don't remember if you flush and when you do go syn what weight would you use on a 289

 

It's generally a good idea to flush the engine if it has a few miles. You don't really have to, but it's a good idea. Also, run the same weight oil as you did before. Generally 10w-30.

 

ok well since its hot as hell here then i can run 10-40

 

Hot as hell huh? You should be so lucky. It's about 10 deg here right now! Try working on your stang in that.

 

it is currently 63* here