That's difficult to say...It all depends on how well the engine was treated and maintained. You could have two exact engines with the same exact mileage, but one will run like s**t and the other will purr like a kitten. One will still have tons of power while the other bogs on the slightest of hills. Same goes for mileage.

 

Hi, not an F-150, but my 2000 Lincoln Navigator has a 4 valve 5.4L engine. Advantage: gets it's torque at a low 2,750 RPM.

 

The 3 valve 5.4 is a piece of crap. Tons of timing issues with this motor. Poor design with cam-phasers, VCT solenoids and plastic chain guides breaking and dropping into your oil pan and clogging your oil pump and starving your engine of oil. The 2 valve has 1 draw back, only 4 threads holding your spark plugs into your cylinder heads. I had a 2001 5.4 2 valve go 175K with no problems and a 2007 5.4 3 valve go 168k with no problems.

Which one was I way more comfortable with and would buy again? The 2 valve every single day of the year. The 3 valve 5.4 is a ticking time bomb.