I purchased a new 2005 Supercab FX4 on friday and have a few questions for those of you who have been breaking in the 5.4L 3V engine. First off, what is the best/most effective way to ensure proper break-in of a new engine; varying RPM's? Through what RPM range? How long should i stay at a constant speed on the highway before varying engine speed?
The other question i have, that is bugging the hell out of me, is what kind of MPG is typical during break-in/or anytime for that matter? I know the way and where you are driving have a big factor in this question. Let's say i take it easy, not too much into the throttle. My truck is running the 3.73 gears, and i do 50/50 city/highway driving. I am still on the initial tank of gas i got at the dealer, and am getting only 210 miles out of 3/4 a tank of gas! This kinda sucks! May be the way i drive, may be something else. I would just like to know what you guys have seen and what you think. Looking into intake and exhaust systems too. What kind of MPG increase have you seen with aftermarket intakes and exhaust

 

I would probably take it easy the first 500 miles. That's the most critical time when parts are getting used to each other and gives everything a chance to mesh. Make sure you change your oil on time, I would even change it after 1000 miles but that is just me. Enjoy the new truck! I know I am with mine!

 

Gas milage will improve in a few thousand miles as it all breaks in...no worries.

 

Thanks for the info guys! Let's hope that the holiday season brings more money for upgrades.......and fuel with the mileage i am getting now!