help with ecomodding a long bed crew cab Frontier

[ModelE]

okay so i'm looking to get my 16.8mpg average on my fronty up a bit...
what are the easiest ecomods to start with?
i'm looking to build a tonneau cover (among other things).. is it better to build a full one or partial? and if partial which end to start at (cab or tailgate)? and materials/methods for the cover itself would be much appreciated

i know that this topic has been discussed over and over, and i apologize

just for the record its a long bed crew cab 4x4... and i already have the grille blocked just about as much as i can get it

[cighon]

when the weather breaks i will be making a aero cap for my frontier. then a partial grill block, removeing the mudflaps and go from there.

[5speed5]

How about smooth hubcaps?

Racing Disc Hubcaps (Pop-On). Scion Hubcaps, Vintage, Kustom Wheel Covers

I'm planning on getting those for my '05 Colorado.