2010 Toyota Tundra 4x4 Double Cab 5.7 MPG Insights...
 

So basically i am looking to possible purchase a newer generation ie: 2010+ Toyota Tundra Double Cab 4x4 5.7L 6 speed auto.

However before doing so i want to check with the gurus here and see if it is possible to achieve better than OEM/EPA ratings.

With that regard the truck in question that I am thinking about is rated for 13 City and 17 Highway.

So my question is do you believe it is possible to attain 17 City and 20 Highway.

My anticipated modifications would likely be the following.

Aero Bed Shell (DIY Kammback style)
Folded Mirrors
Max Out Tire Pressure
Front Air Dam
Front Grill Block
Full Flat Bottom
Rear Fender Well Skirts (maybe)
Smooth Wheel Disks (maybe)
Scan Gauge


Please let me know what you thoughts are.

Seems doable.

The city will be the hard part, nothing you add is going to help. It will be all about driving style there. Driving style, speed, and nothing else should take you to 20 highway as well. Just drive the stock truck at 55-60 mph down the highway and I bet it does 20 mpg all day.

Aero Bed Shell (DIY Kammback style)
Folded Mirrors
Max Out Tire Pressure
Front Air Dam
Front Grill Block
Full Flat Bottom
Rear Fender Well Skirts (maybe)
Smooth Wheel Disks (maybe)
Scan Gauge

Quite the list, but wouldn't be needed just to hit 20 MPG highway.
For your stated vehicle and goals I would do:
***Good driving style.
*The custom bed shell
*Don't worry about folding the mirrors, just run standard (non towing) mirrors.
*Pick a relatively LRR street tire tread, preferably relatively narrow and tall (e.g. 235/85R16), but not max out the PSI. Run the PSI to get decent wear characteristics.
*Definitely front air dam.
*Don't do a massive grill block with an auto transmission. You better have accurate instrumentation (real gauges or OBD-ii readings, not the stock cluster) and a way to quickly remove the block if needed.
*Yes to flat bottom, but NOT under the exhaust.
*Fender Skirts/Smooth Disks- I would look to see if there is a relatively smooth factory wheel option and run that.
*Scanguage, Ultragauge, or similar. I ran an ultragauge on my 2005 Tacoma and loved it.

You should be well above 20MPG highway with that list. I don't do as much city driving as others, but for city driving I would suggest also looking at weight reduction and add double emphasis on driving style.

An half-tonneau would be almost as effective as the aerocap, require less fabrication, and be invisible from below bed height.

The full flat bottom should end in a difusser.

city/HWY
 

I'm also doubtful about improved CITY mpg.Mass,starts,stops,idling,aren't your friend.Aero is essentially meaningless.
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As to HWY mpg,then if you do your list,I'd be very surprised if you didn't make your goal.
I've seen up to 12-mpg added on the highway,and that's with a 900-lb weight penalty.

what do you mean half-tonneau?

half-tonneau
 

looks like freebeard's tied up,so I'll butt in.
General Motors patented a half-tonneau in the 1980s which actually produced lower drag than a full tonneau cover.
Later,Texas Tech found that this half cover,in conjunction with a cab-wing extension of proper length and angle,could produce a drag reduction almost as significant as the GM 'aeroshell'.An 18% vs 20% drag reduction.
This combo is lighter and a lot more simple to fabricate if weather tightness and security aren't as important a priority.
A number of us here at Ecomodder have tried them and can vouch for their performance.

Do you REALLY need (a vehicle like) it ?

The easiest mod is to buy something more fuel efficient that fits the purpose

There's easiest, and then there's Spirit of Ecomodder. ;)