In doing some research on a new or slightly used Expy EL, I discovered the Navigator L, didn't know they made a stretch version. Anyway, also noticed the torque peak on the Navigator (at least for 2006 model) is reported to be lower in RPM band than the Expedition. Also, Lincoln suggests premium fuel, and don't thinkg the Ford does. So, what's the difference in these engines? Can you run reg or mid-grade in the Navigator?
After seeing your replies, I noticed I was looking at previous years Navigators, like 2004/5. On msnautos.com, the stats section showed the peak torque lower rpm (1k lower to reach peak torque for the Navi than the Expy, but the review also said the manual suggests running the Navi on 91 Premium, but they didn't have any issues w/ mid-grade 89. Now that I went and looked up 2008 - it's the same peak torque and @ same RPM as in the Ford, so if there was a diff in the motors it was prior models, like 2005 or older.