Oil Question

[tharimrattler]

I have a 1988 Ford Thunderbird and I was just wondering which motor oil I should use in it (5w-40,10w-40, 20w-40 etc.) the specs are:
v8 5.0
automatic
128,000 miles

Thanks in advance to anyone who helps. :)

[fordtbird88]

i have same car and i use 40