Having trouble getting past 7.4 mpg on my 2007 5.4 3v it also has roush charger it has only done 54,000 , truck runs fine no engine lights no codes when scanned I had a previous issue with it not boosting right but this is now solved, left battery off for a reset a week ago and not gone above 2000rpm and still sat at 7.4mpg on the dash reading, parts I've changed so far

Obx longtube headers with sports cats
Autolite ht0 plugs from jdm as it has the jdm 10 psi pully upgrade kit
Roush air filter
Fuel filter
Full service all oils including engine, diffs and transfer case
All 4 O2 sensors replaced with oem motorcraft
Throttle body motor
All engine pullys and tensioners and belts

Previous owner replaced all the cam parts and chains, guides, lifters, rockers, welling oil pump back in 2018

So at the moment I'm really stumped with why the mpg is so low any help would be much appreciated.

 

Have you crosschecked by doing the math at fillups?

How about following up on your other thread and let us know what was wrong?

https://www.f150online.com/forums/20...very-lazy.html

 

Calculated come in at roughly 10mpg as to roughly 45 liters I'll be lucky to see 100 miles this is in UK liters.

So in us gallons that's 11 to 100 miles so 9.1 mpg it will work out in the US

Yes sorry forgot about other thread just updated.