I've been thinking about acquiring a 2005-2006 Lincoln Navigator and I was curious about the fuel requirement. I see that the Navigators are supposed to use premium 91 octane. Why is that? I know the previous 4-Valve Navigators had a high compression ratio and required the good gas. However, I was under the impression that the 05-06 'Gator used the exact same 3 Valve 5.4L as the Expy which only requires 87 octane. I know the Navigator has a different (6 speed) tranny than the Expy (4 speed), but that shouldn't affect the octane requirement should it? I would just get an 05-06 Expy Eddie Bauer, but I really don't want a column shifter (silly I know).

Can anyone explain why the 3 valve 5.4L Navigator requires premium gas and the 3 valve 5.4L Expedition can use regular gas? Thanks!

 

Bump.

Nobody else has a clue either?

 

There is no solid reason other than since it was a Lincoln and not a Ford then premium fuel would apply. Doesn't make sense I know. I did read a while back that someone tried using reg fuel in a '05 and there was a difference that was not good.

We had an '04 Navigator and like you said required premium, however our '08 Navi with the same power train as an '05 does not. Go figure.

 

We have a 2000 Navigator with the DOHC 4 valve heads and I'm pretty sure that the newer Navi's have this set up as well. As far as the higher octane is concerned, yes, they do like it better but you can get away with the 87 octane because the EMC will adjust the ignition timing to compensate for the lower values. You just don't have quite the power or fuel economy, but it is negligible. I do put in the premium when I'm towing, but I've never had an engine pinging problem when running on regular with no load.

After doing more research, well, I just don't know what motors the newer Navi's have. If they are indeed using the 3V motors like in the pickups, then that seems a backwards step to me. I kind of like the exlusivity of having a 32v motor in my Lincoln because it is something available only to the Lincoln.

 

Canuck, the 2004 model year was the last for the 4-valve DOHC 5.4L in the Navigator as they went to the 3-valve SOHC in both the Expy and the Navi. However, the premium fuel requirement didn't disappear (at least officially) until the 2007 model year.