2004 Grand Marquis

[FastLane]

I would also add it wouldn't hurt to change the sparkplugs in it. Find out the correct torque value and make sure you use a torque wrench. Thats the biggest down fall of the 4.6. They can launch sparkplugs right out of the cylinder head. The 5.4 were way worse but still happens on the 4.6.

The 4R70W is an ok transmission. GM's 4L60E is way better IMO. My trucks trans is way more refined than the Mustang.

 

[Anduril]

You could probably run baby oil in that engine and it wouldn't care. I'm running Supertech High Mileage Synthetic in my Mustang with the same engine.