does it take 10 30weight
5W-30 or 10W-30 will be fine
from everything I have read, the tolerances in the 4.6L Intech in the Mark VIII are so close and perfect that anything over 5W is too heavy...
and I have one with 329,000 miles on it, and I use 5W30 synthetic and it still goes like a champ, and burns no oil.
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