Fuel filter. Esp if you live where there's a solid cold winter, wax buildup in fuel filter/separator will cut economy, and worse, if it reduces flow to cp4 hpfp, can be a setup for fi problems. I change my fuel filter EVERY spring b/c I do see some gain back with the change and we're <30F most of the winter. Regular maitenance is a big part of keeping an EcoD reliable...Hey all, sorry if this has already been asked, I looked some and didnt see it. Anyways got my 2014 eco about 3 years ago. (First time owning a diesel) anyways always averaged around 24mpg, then after first update it dropped to 19 or so, then second update it dropped to around 18. Same as my brothers hemi... and had lost all power.. started looking into things and seen on here about tunes. Got the SKT and as promised I got my power back and my mpg increased to 23mpg. Happy with the increase, but I see on here everyone with a tune seems to be getting 24 to 27 or better? Everything else with truck is factory. Cleaned my EGR when I did the tune, what else should I check or clean to try and improve my mpg? Also did oil change and fuel and air filter. Thanks in advance.