Oil Selection

I have a 89 Mustang LX. Of course with many mods, such as alum heads, rollarrocker, 70mm intake manifold, cam, and much more. This is all on a brand new 302 block. I bought it from a previous owner who was using 20w-50, but as time came for the oil change I decided to look around. From 2 sources I heard to use 5w-30 synthetic and keep it all year. Which would keep my engine lubricated the best.

Was this a correct choice? Other than knowing its going to eat oil. Possibly should I look to change it in the hotter months?

Well, I dont know about you other guys, but I dont like synthetics. My car has almost 200K on it, and supposedly, the guy before me had a "new" motor put in. Not too sure what that means, but due to a suspected head gasket leak, I will soon find out how the internals look... I use a SAE 30 in the winter, and put 40 weight with a qt of Lucas oil stabalizer in for the hotter summer months. Keeps my oil pressure gauge about 3/4 up all year....

10W-30 Mobile 1 would be fine. If the internals have tighter clearances use 5W-30. 20W-50 is too thick for cold starts, even in the summer.

20w50 is old race motor techolegy.when motors are built it depends on the tolerences between moving parts in your case the rebuilt motor probably calls for 30 weight and you can call the manufactures of your aftermarket parts to see what wieght oil but they are ussualy designed for the motor they are going on.
in 1989 i belive all fords call for 5w30
i swear on synthetic oil and in the winter you can try 0w30 for those cold days,and in the summer if you want you can bump it up to a 40wieght if you want
some will argue 10w40 is to thick but im shaw i think the owners manuel will tell you in the summer you can run 10w40.
running to thick of oil will starve certin parts of lubercation starting w/ you cam shaft(so i was told)